Light-emitting device and electronic device

ABSTRACT

Provided is a light-emitting device that can display an image with a wide color gamut or a novel light-emitting element. The light-emitting device includes a plurality of light-emitting elements each of which includes an EL layer between a pair of electrodes. Light obtained from a first light-emitting element through a first color filter has, on chromaticity coordinates (x, y), a chromaticity x of greater than 0.680 and less than or equal to 0.720 and a chromaticity y of greater than or equal to 0.260 and less than or equal to 0.320. Light obtained from a second light-emitting element through a second color filter has, on chromaticity coordinates (x, y), a chromaticity x of greater than or equal to 0.130 and less than or equal to 0.250 and a chromaticity y of greater than 0.710 and less than or equal to 0.810. Light obtained from a third light-emitting element through a third color filter has, on chromaticity coordinates (x, y), a chromaticity x of greater than or equal to 0.120 and less than or equal to 0.170 and a chromaticity y of greater than or equal to 0.020 and less than 0.060.

This application is a continuation of copending U.S. application Ser.No. 15/598,537, filed on May 18, 2017 which is incorporated herein byreference.

TECHNICAL FIELD

One embodiment of the present invention relates to a light-emittingelement, a light-emitting device, and an electronic device. Note thatone embodiment of the present invention is not limited thereto. That is,one embodiment of the present invention relates to an object, a method,a manufacturing method, or a driving method. One embodiment of thepresent invention relates to a process, a machine, manufacture, or acomposition of matter. As specific examples, a semiconductor device, adisplay device, a liquid crystal display device, a lighting device, andthe like can be given.

BACKGROUND ART

A light-emitting element including an EL layer between a pair ofelectrodes (also referred to as an organic EL element) hascharacteristics such as thinness, light weight, high-speed response toinput signals, and low power consumption; thus, a display including sucha light-emitting element has attracted attention as a next-generationflat panel display.

In a light-emitting element, voltage application between a pair ofelectrodes causes, in an EL layer, recombination of electrons and holesinjected from the electrodes, which brings a light-emitting substance(organic compound) contained in the EL layer into an excited state.Light is emitted when the light-emitting substance returns to the groundstate from the excited state. The excited state can be a singlet excitedstate (S*) or a triplet excited state (T*). Light emission from asinglet excited state is referred to as fluorescence, and light emissionfrom a triplet excited state is referred to as phosphorescence. Thestatistical generation ratio of S* to T* in the light-emitting elementis considered to be 1:3. Since the spectrum of light emitted from alight-emitting substance depends on the light-emitting substance, theuse of different types of organic compounds as light-emitting substancesmakes it possible to obtain light-emitting elements which exhibitvarious colors.

To display a full-color image on a display, for example, light-emittingelements of at least three colors of red, green, and blue are necessary.Furthermore, the light-emitting elements are required to consume lowpower.

Examples of specific methods for displaying a full-color image are asfollows: so-called side-by-side patterning in which light-emittingelements that emit light with different colors are separately formed; awhite-color filter method in which a white light-emitting element isused in combination with a color filter; and a color conversion methodin which a light-emitting element that emits monochromatic light, suchas a blue light-emitting element, is used in combination with a colorconversion filter. Each of the methods has advantages and disadvantages.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2007-053090

DISCLOSURE OF INVENTION

Compared with side-by-side patterning, a white-color filter method,which is a specific method for displaying a full-color image,facilitates high resolution because a plurality of light-emittingelements share one EL layer, and is suitable particularly for the marketof displays.

Since light-emitting elements emitting red light, green light, and bluelight utilize white light emitted from a common EL layer in awhite-color filter method, a display with a wide color gamut can beobtained by setting the chromaticities (x, y) of emission colors of thelight-emitting elements in desired ranges.

Thus, in one embodiment of the present invention, a light-emittingdevice that can display an image with a wide color gamut can beprovided. In one embodiment of the present invention, a novellight-emitting element can be provided. In one embodiment of the presentinvention, a light-emitting element with high color purity can beprovided.

Note that the description of these objects does not preclude theexistence of other objects. In one embodiment of the present invention,there is no need to achieve all the objects. Other objects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

One embodiment of the present invention is a light-emitting deviceincluding a plurality of light-emitting elements each of which includesan EL layer between a pair of electrodes. Light emitted from a firstlight-emitting element has, on CIE1931 chromaticity coordinates (x, y)(hereinafter, simply referred to as chromaticity coordinates (x, y)), achromaticity x of greater than 0.680 and less than or equal to 0.720 anda chromaticity y of greater than or equal to 0.260 and less than orequal to 0.320, light emitted from a second light-emitting element has achromaticity x of greater than or equal to 0.130 and less than or equalto 0.250 and a chromaticity y of greater than 0.710 and less than orequal to 0.810, and light emitted from a third light-emitting elementhas a chromaticity x of greater than or equal to 0.120 and less than orequal to 0.170 and a chromaticity y of greater than or equal to 0.020and less than 0.060.

Another embodiment of the present invention is a light-emitting deviceincluding a plurality of light-emitting elements each of which includesan EL layer between a reflective electrode and a transflectiveelectrode. Light emitted from a first light-emitting element has, onchromaticity coordinates (x, y), a chromaticity x of greater than 0.680and less than or equal to 0.720 and a chromaticity y of greater than orequal to 0.260 and less than or equal to 0.320, light emitted from asecond light-emitting element has a chromaticity x of greater than orequal to 0.130 and less than or equal to 0.250 and a chromaticity y ofgreater than 0.710 and less than or equal to 0.810, and light emittedfrom a third light-emitting element has a chromaticity x of greater thanor equal to 0.120 and less than or equal to 0.170 and a chromaticity yof greater than or equal to 0.020 and less than 0.060.

Another embodiment of the present invention is a light-emitting deviceincluding a plurality of light-emitting elements each of which includesan EL layer between a pair of electrodes. Light obtained from a firstlight-emitting element through a first color filter has, on CIE1931chromaticity coordinates, a chromaticity x of greater than 0.680 andless than or equal to 0.720 and a chromaticity y of greater than orequal to 0.260 and less than or equal to 0.320, light obtained from asecond light-emitting element through a second color filter has, on theCIE1931 chromaticity coordinates, a chromaticity x of greater than orequal to 0.130 and less than or equal to 0.250 and a chromaticity y ofgreater than 0.710 and less than or equal to 0.810, and light obtainedfrom a third light-emitting element through a third color filter has, onthe CIE1931 chromaticity coordinates, a chromaticity x of greater thanor equal to 0.120 and less than or equal to 0.170 and a chromaticity yof greater than or equal to 0.020 and less than 0.060.

Another embodiment of the present invention is a light-emitting deviceincluding a plurality of light-emitting elements each of which includesan EL layer between a reflective electrode and a transflectiveelectrode. Light obtained from a first light-emitting element through afirst color filter has, on CIE1931 chromaticity coordinates, achromaticity x of greater than 0.680 and less than or equal to 0.720 anda chromaticity y of greater than or equal to 0.260 and less than orequal to 0.320, light obtained from a second light-emitting elementthrough a second color filter has, on the CIE1931 chromaticitycoordinates, a chromaticity x of greater than or equal to 0.130 and lessthan or equal to 0.250 and a chromaticity y of greater than 0.710 andless than or equal to 0.810, and light obtained from a thirdlight-emitting element through a third color filter has, on the CIE1931chromaticity coordinates, a chromaticity x of greater than or equal to0.120 and less than or equal to 0.170 and a chromaticity y of greaterthan or equal to 0.020 and less than 0.060.

In any of the above structures, the EL layers included in the firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element are preferably EL layers that emit white lightand that are formed using the same material. Each of the EL layersincludes at least a light-emitting layer. A plurality of EL layers maybe included in each light-emitting element, and the EL layers may bestacked with a charge generation layer positioned therebetween.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, and a third light-emitting element each of which includes an ELlayer between a pair of electrodes. The EL layers emit white light.Light obtained from the first light-emitting element through a firstcolor filter has, on CIE1931 chromaticity coordinates, a chromaticity xof greater than 0.680 and less than or equal to 0.720 and a chromaticityy of greater than or equal to 0.260 and less than or equal to 0.320,light obtained from the second light-emitting element through a secondcolor filter has, on the CIE1931 chromaticity coordinates, achromaticity x of greater than or equal to 0.130 and less than or equalto 0.250 and a chromaticity y of greater than 0.710 and less than orequal to 0.810, and light obtained from the third light-emitting elementthrough a third color filter has, on the CIE1931 chromaticitycoordinates, a chromaticity x of greater than or equal to 0.120 and lessthan or equal to 0.170 and a chromaticity y of greater than or equal to0.020 and less than 0.060.

To extract light with different colors efficiently from the EL layersthat emit white light in the light-emitting elements, optical pathlengths between the pair of electrodes are preferably adjusted dependingon the emission color to form what is called a microcavity structure.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, and a third light-emitting element each of which includes an ELlayer between a reflective electrode and a transflective electrode. TheEL layers emit white light. Light obtained from the first light-emittingelement through a first color filter has, on CIE1931 chromaticitycoordinates, a chromaticity x of greater than 0.680 and less than orequal to 0.720 and a chromaticity y of greater than or equal to 0.260and less than or equal to 0.320, light obtained from the secondlight-emitting element through a second color filter has, on the CIE1931chromaticity coordinates, a chromaticity x of greater than or equal to0.130 and less than or equal to 0.250 and a chromaticity y of greaterthan 0.710 and less than or equal to 0.810, and light obtained from thethird light-emitting element through a third color filter has, on theCIE1931 chromaticity coordinates, a chromaticity x of greater than orequal to 0.120 and less than or equal to 0.170 and a chromaticity y ofgreater than or equal to 0.020 and less than 0.060.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, and a third light-emitting element each of which includes an ELlayer between a pair of electrodes. Each of the EL layers emits whitelight and includes a first EL layer and a second EL layer that arestacked with a charge generation layer positioned therebetween. Thefirst EL layer contains a red light-emitting substance and a greenlight-emitting substance. The second EL layer contains a bluelight-emitting substance. Light obtained from the first light-emittingelement through a first color filter has, on CIE1931 chromaticitycoordinates, a chromaticity x of greater than 0.680 and less than orequal to 0.720 and a chromaticity y of greater than or equal to 0.260and less than or equal to 0.320, light obtained from the secondlight-emitting element through a second color filter has, on the CIE1931chromaticity coordinates, a chromaticity x of greater than or equal to0.130 and less than or equal to 0.250 and a chromaticity y of greaterthan 0.710 and less than or equal to 0.810, and light obtained from thethird light-emitting element through a third color filter has, on theCIE1931 chromaticity coordinates, a chromaticity x of greater than orequal to 0.120 and less than or equal to 0.170 and a chromaticity y ofgreater than or equal to 0.020 and less than 0.060.

Another embodiment of the present invention is a light-emitting deviceincluding a first light-emitting element, a second light-emittingelement, and a third light-emitting element each of which includes an ELlayer between a reflective electrode and a transflective electrode. Eachof the EL layers emits white light and includes a first EL layer and asecond EL layer that are stacked with a charge generation layerpositioned therebetween. The first EL layer contains a redlight-emitting substance and a green light-emitting substance. Thesecond EL layer contains a blue light-emitting substance. Light obtainedfrom the first light-emitting element through a first color filter has,on CIE1931 chromaticity coordinates, a chromaticity x of greater than0.680 and less than or equal to 0.720 and a chromaticity y of greaterthan or equal to 0.260 and less than or equal to 0.320, light obtainedfrom the second light-emitting element through a second color filterhas, on the CIE1931 chromaticity coordinates, a chromaticity x ofgreater than or equal to 0.130 and less than or equal to 0.250 and achromaticity y of greater than 0.710 and less than or equal to 0.810,and light obtained from the third light-emitting element through a thirdcolor filter has, on the CIE1931 chromaticity coordinates, achromaticity x of greater than or equal to 0.120 and less than or equalto 0.170 and a chromaticity y of greater than or equal to 0.020 and lessthan 0.060.

In any of the structures including the reflective electrode and thetransflective electrode, an optical path length between the reflectiveelectrode and the transflective electrode in the first light-emittingelement may be set so that emission intensity of red light can beincreased. An optical path length between the reflective electrode andthe transflective electrode in the second light-emitting element may beset so that emission intensity of green light may be increased. Anoptical path length between the reflective electrode and thetransflective electrode in the third light-emitting element may be setso that emission intensity of blue light may be increased.

In any of the structures, the first color filter may have a 600-nm lighttransmittance of less than or equal to 60% and a 650-nm lighttransmittance of greater than or equal to 70%. The second color filtermay have a 480-nm light transmittance of less than or equal to 60%, a580-nm light transmittance of less than or equal to 60%, and a 530-nmlight transmittance of greater than or equal to 70%. The third colorfilter may have a 510-nm light transmittance of less than or equal to60% and a 450-nm light transmittance of greater than or equal to 70%.

In any of the structures, the light obtained from the firstlight-emitting element through the first color filter may have anemission spectrum whose peak value is within a range from 620 nm to 680nm.

Another embodiment of the present invention is an electronic device thatincludes the light-emitting device of one embodiment of the presentinvention and an operation key, a speaker, a microphone, or an externalconnection portion.

One embodiment of the present invention includes, in its category, inaddition to a light-emitting device including a light-emitting element,an electronic device including a light-emitting element or alight-emitting device (specifically, an electronic device including alight-emitting element or a light-emitting device and a connectionterminal or an operation key) and a lighting device including alight-emitting element or a light-emitting device (specifically, alighting device including a light-emitting element or a light-emittingdevice and a housing). Accordingly, a light-emitting device in thisspecification means an image display device or a light source (includinga lighting device). Furthermore, a light-emitting device includes thefollowing modules in its category: a module in which a connector such asa flexible printed circuit (FPC) or a tape carrier package (TCP) isattached to a light-emitting device; a module having a TCP whose end isprovided with a printed wiring board; and a module in which anintegrated circuit (IC) is directly mounted on a light-emitting elementby a chip on glass (COG) method.

One embodiment of the present invention can provide a light-emittingdevice that can display an image with a wide color gamut. One embodimentof the present invention can provide a novel light-emitting element. Oneembodiment of the present invention can provide a light-emitting elementwith high color purity. One embodiment of the present invention canprovide a light-emitting device with high color reproducibility. Oneembodiment of the present invention can provide an electronic deviceincluding a display portion with high color reproducibility.

Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot necessarily have all the effects listed above. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C illustrate light-emitting devices of one embodiment ofthe present invention.

FIGS. 2A to 2D each illustrate a structure of a light-emitting element.

FIGS. 3A and 3B illustrate a light-emitting device.

FIGS. 4A and 4B illustrate a light-emitting device.

FIGS. 5A, 5B, 5C, 5D, 5D′-1, and 5D′-2 illustrate electronic devices.

FIGS. 6A to 6C illustrate an electronic device.

FIGS. 7A and 7B illustrate an automobile.

FIGS. 8A to 8D each illustrate a lighting device.

FIG. 9 illustrates lighting devices.

FIGS. 10A and 10B illustrate an example of a touch panel.

FIGS. 11A and 11B illustrate an example of a touch panel.

FIGS. 12A and 12B illustrate an example of a touch panel.

FIGS. 13A and 13B are a block diagram and a timing chart of a touchsensor.

FIG. 14 is a circuit diagram of a touch sensor.

FIGS. 15A, 15B1, and 15B2 illustrate block diagrams of display devices.

FIG. 16 illustrates a circuit configuration of a display device.

FIG. 17 illustrates a cross-sectional structure of a display device.

FIG. 18 illustrates a light-emitting element.

FIG. 19 shows the luminance-current density characteristics oflight-emitting elements 1 to 4.

FIG. 20 shows the luminance-voltage characteristics of thelight-emitting elements 1 to 4.

FIG. 21 shows the current efficiency-luminance characteristics of thelight-emitting elements 1 to 4.

FIG. 22 shows the current-voltage characteristics of the light-emittingelements 1 to 4.

FIG. 23 shows the emission spectra of the light-emitting elements 1 to4.

FIG. 24 shows the transmission spectra of color filters.

FIG. 25 shows the luminance-current density characteristics oflight-emitting elements 5 to 8.

FIG. 26 shows the luminance-voltage characteristics of thelight-emitting elements 5 to 8.

FIG. 27 shows the current efficiency-luminance characteristics of thelight-emitting elements 5 to 8.

FIG. 28 shows the current-voltage characteristics of the light-emittingelements 5 to 8.

FIG. 29 shows the emission spectra of the light-emitting elements 5 to8.

FIG. 30 illustrates a light-emitting element.

FIG. 31 shows the luminance-current density characteristics oflight-emitting elements 9 to 11.

FIG. 32 shows the luminance-voltage characteristics of thelight-emitting elements 9 to 11.

FIG. 33 shows the current efficiency-luminance characteristics of thelight-emitting elements 9 to 11.

FIG. 34 shows the current-voltage characteristics of the light-emittingelements 9 to 11.

FIG. 35 shows the emission spectra of the light-emitting elements 9 to11.

FIG. 36 shows the CIE1931 chromaticity coordinates (x,y chromaticitycoordinates).

FIG. 37 shows the CIE1976 chromaticity coordinates (u′,v′ chromaticitycoordinates).

FIG. 38 shows the luminance-current density characteristics oflight-emitting elements.

FIG. 39 shows the luminance-voltage characteristics of light-emittingelements.

FIG. 40 shows the current efficiency-luminance characteristics oflight-emitting elements.

FIG. 41 shows the current-voltage characteristics of light-emittingelements.

FIG. 42 shows the emission spectra of light-emitting elements.

FIG. 43 shows the reliability of light-emitting elements.

FIG. 44 shows the emission spectra of light-emitting elements.

FIG. 45 shows the CIE1931 chromaticity coordinates (x,y chromaticitycoordinates).

FIG. 46 shows the relationships between external quantum efficiency andcurrent density.

FIG. 47 shows the results of driving tests (25° C.) of light-emittingelements.

FIG. 48 shows the results of driving tests (85° C.) of light-emittingelements.

FIG. 49 shows the results of high-temperature preservation tests of alight-emitting element.

FIG. 50 shows the emission spectra of light-emitting elements.

FIG. 51 shows the relationships between external quantum efficiency andluminance.

FIG. 52 shows the results of driving tests (25° C.) of light-emittingelements.

FIG. 53 shows the results of driving tests (85° C.) of light-emittingelements.

FIG. 54 shows the results of high-temperature preservation tests of alight-emitting element.

FIG. 55 shows the CIE1976 chromaticity coordinates (u′,v′ chromaticitycoordinates).

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the drawings. However, the present invention is notlimited to the following description, and the mode and details can bevariously changed unless departing from the scope and spirit of thepresent invention. Thus, the present invention should not be construedas being limited to the description in the following embodiments.

Note that the position, the size, the range, or the like of eachcomponent illustrated in the drawings and the like are not accuratelyrepresented in some cases for easy understanding. Therefore, thedisclosed invention is not necessarily limited to the position, size,range, or the like as disclosed in the drawings and the like.

In the description of structures of the present invention in thisspecification and the like with reference to the drawings, the samecomponents in different drawings are denoted by the same referencenumeral.

Embodiment 1

In this embodiment, light-emitting devices of one embodiment of thepresent invention will be described with reference to FIGS. 1A and 1B.

A light-emitting device illustrated in FIG. 1A includes a firstlight-emitting element 105R, a second light-emitting element 105G, and athird light-emitting element 105B. The first light-emitting element 105Rincludes a first electrode 101, an EL layer 103R, and a second electrode102. The second light-emitting element 105G includes the first electrode101, an EL layer 103G, and the second electrode 102. The thirdlight-emitting element 105B includes the first electrode 101, an ELlayer 103B, and the second electrode 102. Note that the EL layers (103R,103G, and 103B) included in the light-emitting elements containdifferent materials partly or entirely and are formed by a separatecoloring method. This means that, for example, the EL layer 103R can bean EL layer that emits red light, the EL layer 103G can be an EL layerthat emits green light, and the EL layer 103B can be an EL layer thatemits blue light.

At least one of the electrodes (in the cases of FIGS. 1A and 1B, thesecond electrode 102 in the arrow direction in which light is emittedfrom the EL layer) included in each of the light-emitting elements ispreferably formed using a light-transmitting electrode material.

A light-emitting device illustrated in FIG. 1B includes the firstlight-emitting element 105R, the second light-emitting element 105G, andthe third light-emitting element 105B. The first light-emitting element105R includes the first electrode 101, an EL layer 103, and the secondelectrode 102. A color filter 104R is provided in a region overlappingwith the first electrode 101, the EL layer 103, and the second electrode102. The second light-emitting element 105G includes the first electrode101, the EL layer 103, and the second electrode 102. A color filter 104Gis provided in a region overlapping with the first electrode 101, the ELlayer 103, and the second electrode 102. The third light-emittingelement 105B includes the first electrode 101, the EL layer 103, and thesecond electrode 102. A color filter 104B is provided in a regionoverlapping with the first electrode 101, the EL layer 103, and thesecond electrode 102. Note that the light-emitting elements include thesame EL layer 103.

The second electrode 102 included in each of the light-emitting elementsillustrated in FIG. 1B is preferably formed using a light-transmittingelectrode material. Accordingly, red light 106R of light emitted fromthe EL layer 103 can be extracted from the first light-emitting element105R to the outside through the color filter 104R. Furthermore, greenlight 106G of the light emitted from the EL layer 103 can be extractedfrom the second light-emitting element 105G to the outside through thecolor filter 104G. In addition, blue light 106B of the light emittedfrom the EL layer 103 can be extracted from the third light-emittingelement 105B to the outside through the color filter 104B. This meansthat the color filter 104R has a function of transmitting red light, thecolor filter 104G has a function of transmitting green light, and thecolor filter 104B has a function of transmitting blue light.

Although not illustrated in FIGS. 1A and 1B, each of the firstlight-emitting element 105R, the second light-emitting element 105G, andthe third light-emitting element 105B in the light-emitting devicedescribed in this embodiment may be electrically connected to atransistor that controls light emission.

The EL layers (103, 103R, 103G, and 103B) illustrated in FIGS. 1A and 1Beach include functional layers such as a light-emitting layer containinga light-emitting substance, a hole-injection layer, a hole-transportlayer, an electron-transport layer, and an electron-injection layer. Inthe case of stacked EL layers, a charge generation layer is positionedbetween the EL layers.

The light-emitting layers included in the EL layers (103, 103R, 103G,and 103B) illustrated in FIGS. 1A and 1B can contain one or more kindsof organic compounds in addition to the light-emitting substance. Onelight-emitting layer or the stacked light-emitting layers may containlight-emitting substances of different colors. In the case where the ELlayer (103, 103R, 103G, or 103B) illustrated in FIG. 1A or FIG. 1B isformed of stacked EL layers, a charge generation layer is providedbetween the EL layers as described above. In that case, the EL layerspreferably emit light with different colors.

The first light-emitting element 105R, the second light-emitting element105G, and the third light-emitting element 105B illustrated in FIG. 1Bshare the EL layer 103. In that case, light with different colors can beobtained from the light-emitting elements while the EL layer 103 emitswhite light.

In the case where light emitted from the EL layer 103 is white lightobtained by mixing light with a plurality of wavelengths are mixed asillustrated in FIG. 1B, it is preferable to employ a microcavitystructure by using the first electrode 101 as a reflective electrode andthe second electrode 102 as a transflective electrode to intensify lightwith a specific wavelength. Note that a microcavity structure may beemployed also in the case where the EL layers are separately formed foreach light-emitting element as illustrated in FIG. 1A.

Since the first light-emitting element 105R illustrated in FIG. 1A orFIG. 1B is a light-emitting element that emits red light, the thicknessof the first electrode 101 is preferably adjusted so that an opticalpath length between the first electrode 101 and the second electrode 102may be set to an optical path length that increases the emissionintensity of red light. Furthermore, since the second light-emittingelement 105G is a light-emitting element that emits green light, thethickness of the first electrode 101 is preferably adjusted so that anoptical path length between the first electrode 101 and the secondelectrode 102 may be set to an optical path length that increases theemission intensity of green light. In addition, since the thirdlight-emitting element 105B is a light-emitting element that emits bluelight, the thickness of the first electrode 101 is preferably adjustedso that an optical path length between the first electrode 101 and thesecond electrode 102 may be set to an optical path length that increasesthe emission intensity of blue light.

In the case where light emitted from the EL layer 103 is white light asillustrated in FIG. 1B, it is desirable that red light, green light, andblue light that constitute white light have independent emission spectrathat do not overlap with each other to prevent a reduction in colorpurity. The emission spectrum of green light and the emission spectrumof red light are especially likely to overlap with each other becausetheir peak wavelengths are close to each other. The light-emittingsubstances contained in the EL layers and stacked structures of the ELlayers are important in preventing such overlap of the emission spectra.The number of steps can be smaller in the case of light-emitting devicesincluding a common EL layer than in the case of light-emitting devicesincluding separately formed EL layers; however, some difficulties arecaused. Thus, one embodiment of the present invention can provide notonly a light-emitting device having favorable chromaticity for eachemission color, but also a light-emitting device in which overlap ofdifferent emission spectra is prevented and chromaticity for eachemission color is favorable particularly when a common light-emittinglayer that emits white light is included.

The light-emitting device described in this embodiment includes aplurality of light-emitting elements and can display a full-color image.At present, some standards are established as quality indicators forfull-color displays.

For example, the sRGB standard, which is an international standard forcolor spaces defined by the International Electrotechnical Commission(IEC) to standardize color reproduction on devices such as displays,printers, digital cameras, and scanners, is widely used. Note that inthe sRGB standard, the chromaticities (x, y) on the CIE1931 chromaticitycoordinates (x,y chromaticity coordinates) defined by the InternationalCommission on Illumination (CIE) are (0.640, 0.330) for red (R), (0.300,0.600) for green (G), and (0.150, 0.060) for blue (B).

In the NTSC standard, which is a color gamut standard for analogtelevision systems defined by the National Television System Committee(NTSC) in America, the chromaticities (x, y) are (0.670, 0.330) for red(R), (0.210, 0.710) for green (G), and (0.140, 0.080) for blue (B).

In the DCI-P3 standard (defined by Digital Cinema Initiatives, LLC),which is the international unified standard used when distributingdigital movies (cinema), the chromaticities (x, y) are (0.680, 0.320)for red (R), (0.265, 0.690) for green (G), and (0.150, 0.060) for blue(B).

In the BT.2020 standard for ultra high definition television (UHDTV,also referred to as Super Hi-Vision), which is defined by JapanBroadcasting Corporation (NHK), the chromaticities (x, y) are (0.708,0.292) for red, (0.170, 0.797) for green, and (0.131, 0.046) for blue.

As described above, a variety of standards for displays are defined. Thelight-emitting device of one embodiment of the present inventionincludes light-emitting elements (a light-emitting element that emitsred light, a light-emitting element that emits green light, and alight-emitting element that emits blue light) that cover chromaticityranges (a region A, a region B, and a region C) represented by colorcoordinates in FIG. 1C. Specifically, the light-emitting device includesat least the first light-emitting element 105R from which the red light106R can be obtained, the second light-emitting element 105G from whichthe green light 106G can be obtained, and the third light-emittingelement 105B from which the blue light 106B can be obtained. Lightobtained from the first light-emitting element 105R has chromaticitythat falls within the region A in the color coordinates in FIG. 1C, orhas a chromaticity x of greater than 0.680 and less than or equal to0.720 and a chromaticity y of greater than or equal to 0.260 and lessthan or equal to 0.320 on the CIE1931 chromaticity coordinates. Lightobtained from the second light-emitting element 105G has chromaticitythat falls within the region B in the color coordinates in FIG. 1C, orhas a chromaticity x of greater than or equal to 0.130 and less than orequal to 0.250 and a chromaticity y of greater than 0.710 and less thanor equal to 0.810. Light obtained from the third light-emitting element105B has chromaticity that falls within the region C in the colorcoordinates in FIG. 1C, or has a chromaticity x of greater than or equalto 0.120 and less than or equal to 0.170 and a chromaticity y of greaterthan or equal to 0.020 and less than 0.060. Note that as illustrated inFIG. 1B, a structure in which the light-emitting elements (105R, 105G,and 105B) and the color filters (104R, 104G, and 104B) are used incombination and light emissions obtained from the light-emittingelements (105R, 105G, and 105B) through the color filters (104R, 104G,and 104B) cover the above chromaticity ranges may be employed. Alight-emitting device including such light-emitting elements can providehigh-quality full-color displays. It is needless to say that a structurethat covers the above chromaticity ranges without using color filtersmay be employed as illustrated in FIG. 1A.

Note that the peak wavelength of the emission spectrum of the firstlight-emitting element 105R illustrated in FIG. 1A is preferably greaterthan or equal to 620 nm and less than or equal to 680 nm. The peakwavelength of the emission spectrum of the second light-emitting element105G illustrated in FIG. 1A is preferably greater than or equal to 500nm and less than or equal to 530 nm. The peak wavelength of the emissionspectrum of the third light-emitting element 105B illustrated in FIG. 1Ais preferably greater than or equal to 430 nm and less than or equal to460 nm. The half widths of the emission spectra of the light-emittingelements 105R, 105G, and 105B are preferably greater than or equal to 5nm and less than or equal to 45 nm, greater than or equal to 5 nm andless than or equal to 35 nm, and greater than or equal to 5 nm and lessthan or equal to 25 nm, respectively. The peak wavelengths and the halfwidths of emission spectra of light passed through the color filtersillustrated in FIG. 1B have similar values.

In one embodiment of the present invention, the above chromaticities arepreferably obtained so that the area ratio to the BT.2020 color gamut inthe CIE chromaticity coordinates (x, y) can become higher than or equalto 80%, further preferably higher than or equal to 90%, or the colorgamut coverage can become higher than or equal to 75%, furtherpreferably higher than or equal to 85%.

The chromaticities may be measured with any of a luminance colorimeter,a spectroradiometer, and an emission spectrometer, and it is sufficientthat the above-described chromaticities be met in any one of themeasurements. Note that it is preferable that the above-describedchromaticities be met in all of the measurements.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 2

In this embodiment, light-emitting elements of one embodiment of thepresent invention will be described.

<<Basic Structure of Light-Emitting Element>>

A basic structure of a light-emitting element will be described. FIG. 2Aillustrates a light-emitting element including, between a pair ofelectrodes, an EL layer having a light-emitting layer. Specifically, anEL layer 203 is provided between a first electrode 201 and a secondelectrode 202 (single structure).

FIG. 2B illustrates a light-emitting element that has a stacked-layerstructure (tandem structure) in which a plurality of EL layers (two ELlayers 203 a and 203 b in FIG. 2B) are provided between a pair ofelectrodes and a charge generation layer 204 is provided between the ELlayers. With the use of such a tandem light-emitting element, alight-emitting device which can be driven at low voltage with low powerconsumption can be obtained.

The charge generation layer 204 has a function of injecting electronsinto one of the EL layers (203 a or 203 b) and injecting holes into theother of the EL layers (203 b or 203 a) when voltage is applied betweenthe first electrode 201 and the second electrode 202. Thus, when voltageis applied to the first electrode 201 in FIG. 2B such that the potentialof the first electrode 201 becomes higher than that of the secondelectrode 202, the charge generation layer 204 injects electrons intothe EL layer 203 a and injects holes into the EL layer 203 b.

Note that in terms of light extraction efficiency, the charge generationlayer 204 preferably has a property of transmitting visible light(specifically, a visible light transmittance of 40% or higher).Furthermore, the charge generation layer 204 functions even if it haslower conductivity than the first electrode 201 or the second electrode202.

FIG. 2C illustrates a stacked-layer structure of the EL layer 203 in thelight-emitting element of one embodiment of the present invention. Inthis case, the first electrode 201 is regarded as functioning as ananode. The EL layer 203 has a structure in which a hole-injection layer211, a hole-transport layer 212, a light-emitting layer 213, anelectron-transport layer 214, and an electron-injection layer 215 arestacked in this order over the first electrode 201. Even in the casewhere a plurality of EL layers are provided as in the tandem structureillustrated in FIG. 2B, the layers in each EL layer are sequentiallystacked from the anode side as described above. When the first electrode201 is a cathode and the second electrode 202 is an anode, the stackingorder of the layers is reversed.

The light-emitting layer 213 included in the EL layers (203, 203 a, and203 b) contains light-emitting substances and a plurality of substancesin appropriate combination, so that fluorescence or phosphorescence ofdesired emission colors can be obtained. The light-emitting layer 213may have a stacked-layer structure having different emission colors. Inthat case, light-emitting substances and other substances are differentbetween the stacked light-emitting layers. Alternatively, the pluralityof EL layers (203 a and 203 b) in FIG. 2B may exhibit their respectiveemission colors. Also in that case, light-emitting substances and othersubstances are different between the light-emitting layers.

In the light-emitting element of one embodiment of the presentinvention, for example, a micro optical resonator (microcavity)structure in which the first electrode 201 is a reflective electrode andthe second electrode 202 is a transflective electrode can be employed inFIG. 2C, whereby light emission from the light-emitting layer 213 in theEL layer 203 can be resonated between the electrodes and light emissiontransmitted from the second electrode 202 can be intensified.

Note that when the first electrode 201 of the light-emitting element isa reflective electrode having a structure in which a reflectiveconductive material and a light-transmitting conductive material(transparent conductive film) are stacked, optical adjustment can beperformed by controlling the thickness of the transparent conductivefilm. Specifically, when the wavelength of light from the light-emittinglayer 213 is λ, the distance between the first electrode 201 and thesecond electrode 202 is preferably adjusted to around mλ/2 (m is anatural number).

To amplify desired light (wavelength: λ) obtained from thelight-emitting layer 213, the optical path length from the firstelectrode 201 to a region where desired light is obtained in thelight-emitting layer 213 (light-emitting region) and the optical pathlength from the second electrode 202 to the region where desired lightis obtained in the light-emitting layer 213 (light-emitting region) arepreferably adjusted to around (2m′+1)λ/4 (m′ is a natural number). Here,the light-emitting region means a region where holes and electrons arerecombined in the light-emitting layer 213.

By such optical adjustment, the spectrum of specific monochromatic lightfrom the light-emitting layer 213 can be narrowed and light emissionwith high color purity can be obtained.

In that case, the optical path length between the first electrode 201and the second electrode 202 is, to be exact, the total thickness from areflective region in the first electrode 201 to a reflective region inthe second electrode 202. However, it is difficult to exactly determinethe reflective regions in the first electrode 201 and the secondelectrode 202; thus, it is assumed that the above effect can besufficiently obtained wherever the reflective regions may be set in thefirst electrode 201 and the second electrode 202. Furthermore, theoptical path length between the first electrode 201 and thelight-emitting layer emitting desired light is, to be exact, the opticalpath length between the reflective region in the first electrode 201 andthe light-emitting region where desired light is obtained in thelight-emitting layer. However, it is difficult to precisely determinethe reflective region in the first electrode 201 and the light-emittingregion where desired light is obtained in the light-emitting layer;thus, it is assumed that the above effect can be sufficiently obtainedwherever the reflective region and the light-emitting region may be setin the first electrode 201 and the light-emitting layer emitting desiredlight.

The light-emitting element in FIG. 2C has a microcavity structure, sothat light rays (monochromatic light rays) with different wavelengthscan be extracted even if the same EL layer is used. Thus, separatecoloring for obtaining a plurality of emission colors (e.g., R, G, andB) is not necessary. Therefore, high resolution can be easily achieved.Note that a combination with coloring layers (color filters) is alsopossible. Furthermore, emission intensity of light with a specificwavelength in the front direction can be increased, whereby powerconsumption can be reduced.

In the light-emitting element of one embodiment of the presentinvention, at least one of the first electrode 201 and the secondelectrode 202 is a light-transmitting electrode (e.g., a transparentelectrode or a transflective electrode). In the case where thelight-transmitting electrode is a transparent electrode, the transparentelectrode has a visible light transmittance of higher than or equal to40%. In the case where the light-transmitting electrode is atransflective electrode, the transflective electrode has a visible lightreflectance of higher than or equal to 20% and lower than or equal to80%, and preferably higher than or equal to 40% and lower than or equalto 70%. These electrodes preferably have a resistivity of 1×10⁻² Ωcm orless.

Furthermore, when one of the first electrode 201 and the secondelectrode 202 is a reflective electrode in the light-emitting element ofone embodiment of the present invention, the visible light reflectanceof the reflective electrode is higher than or equal to 40% and lowerthan or equal to 100%, and preferably higher than or equal to 70% andlower than or equal to 100%. This electrode preferably has a resistivityof 1×10⁻² Ωcm or less.

<<Specific Structure and Fabrication Method of Light-Emitting Element>>

Specific structures and specific fabrication methods of light-emittingelements of embodiments of the present invention will be described withreference to FIGS. 2A to 2D. Here, a light-emitting element having thetandem structure in FIG. 2B and a microcavity structure will bedescribed with reference to FIG. 2D. In the light-emitting element inFIG. 2D having a microcavity structure, the first electrode 201 isformed as a reflective electrode and the second electrode 202 is formedas a transflective electrode. Thus, a single-layer structure or astacked-layer structure can be formed using one or more kinds of desiredelectrode materials. Note that the second electrode 202 is formed afterformation of the EL layer 203 b, with the use of a material selected asdescribed above. For fabrication of these electrodes, a sputteringmethod or a vacuum evaporation method can be used.

<First Electrode and Second Electrode>

As materials used for the first electrode 201 and the second electrode202, any of the materials below can be used in an appropriatecombination as long as the functions of the electrodes described abovecan be fulfilled. For example, a metal, an alloy, an electricallyconductive compound, a mixture of these, and the like can beappropriately used. Specifically, an In—Sn oxide (also referred to asITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, anIn—W—Zn oxide, or the like can be used. In addition, it is possible touse a metal such as aluminum (Al), titanium (Ti), chromium (Cr),manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo),tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt),silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing anappropriate combination of any of these metals. It is also possible touse a Group 1 element or a Group 2 element in the periodic table, whichis not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca),or strontium (Sr)), a rare earth metal such as europium (Eu) orytterbium (Yb), an alloy containing an appropriate combination of any ofthese elements, graphene, or the like.

In the light-emitting element in FIG. 2D, when the first electrode 201is an anode, a hole-injection layer 211 a and a hole-transport layer 212a of the EL layer 203 a are sequentially stacked over the firstelectrode 201 by a vacuum evaporation method. After the EL layer 203 aand the charge generation layer 204 are formed, a hole-injection layer211 b and a hole-transport layer 212 b of the EL layer 203 b aresequentially stacked over the charge generation layer 204 in a similarmanner.

<Hole-Injection Layer and Hole-Transport Layer>

The hole-injection layers (211, 211 a, and 211 b) inject holes from thefirst electrode 201 that is an anode or the charge generation layer(204) to the EL layers (203, 203 a, and 203 b) and each contain amaterial with a high hole-injection property.

As examples of the material with a high hole-injection property,transition metal oxides such as molybdenum oxide, vanadium oxide,ruthenium oxide, tungsten oxide, and manganese oxide can be given.Alternatively, it is possible to use any of the following materials:phthalocyanine-based compounds such as phthalocyanine (abbreviation:H₂Pc) and copper phthalocyanine (abbreviation: CuPc); aromatic aminecompounds such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) andN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD); high molecular compounds such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS); and the like.

Alternatively, as the material with a high hole-injection property, acomposite material containing a hole-transport material and an acceptormaterial (an electron-accepting material) can also be used. In thatcase, the acceptor material extracts electrons from a hole-transportmaterial, so that holes are generated in the hole-injection layers (211,211 a, and 211 b) and the holes are injected into the light-emittinglayers (213, 213 a, and 213 b) through the hole-transport layers (212,212 a, and 212 b). Note that each of the hole-injection layers (211, 211a, and 211 b) may be formed to have a single-layer structure using acomposite material containing a hole-transport material and an acceptormaterial (electron-accepting material), or a stacked-layer structure inwhich a layer including a hole-transport material and a layer includingan acceptor material (electron-accepting material) are stacked.

The hole-transport layers (212, 212 a, and 212 b) transport the holes,which are injected from the first electrode 201 by the hole-injectionlayers (211, 211 a, and 211 b), to the light-emitting layers (213, 213a, and 213 b). Note that the hole-transport layers (212, 212 a, and 212b) each contain a hole-transport material. It is particularly preferablethat the HOMO level of the hole-transport material included in thehole-transport layers (212, 212 a, and 212 b) be the same as or close tothat of the hole-injection layers (211, 211 a, and 211 b).

Examples of the acceptor material used for the hole-injection layers(211, 211 a, and 211 b) include an oxide of a metal belonging to any ofGroup 4 to Group 8 of the periodic table. Specifically, molybdenumoxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,tungsten oxide, manganese oxide, and rhenium oxide can be given. Amongthese, molybdenum oxide is especially preferable since it is stable inthe air, has a low hygroscopic property, and is easy to handle.Alternatively, organic acceptors such as a quinodimethane derivative, achloranil derivative, and a hexaazatriphenylene derivative can be used.Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane(abbreviation: F₄-TCNQ), chloranil,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), or the like can be used.

The hole-transport materials used for the hole-injection layers (211,211 a, and 211 b) and the hole-transport layers (212, 212 a, and 212 b)are preferably substances with a hole mobility of greater than or equalto 10⁻⁶ cm²/Vs. Note that other substances may be used as long as thesubstances have a hole-transport property higher than anelectron-transport property.

Preferred hole-transport materials are π-electron rich heteroaromaticcompounds (e.g., carbazole derivatives and indole derivatives) andaromatic amine compounds, examples of which include compounds having anaromatic amine skeleton, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPPn),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF),N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF),4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA); compounds having a carbazole skeleton, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP),3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene(abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA);compounds having a thiophene skeleton, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having a furan skeleton, suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II).

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Note that the hole-transport material is not limited to the aboveexamples and may be one of or a combination of various known materialswhen used for the hole-injection layers (211, 211 a, and 211 b) and thehole-transport layers (212, 212 a, and 212 b). Note that thehole-transport layers (212, 212 a, and 212 b) may each be formed of aplurality of layers. That is, for example, the hole-transport layers mayeach have a stacked-layer structure of a first hole-transport layer anda second hole-transport layer.

In the light-emitting element in FIG. 2D, the light-emitting layer 213 ais formed over the hole-transport layer 212 a of the EL layer 203 a by avacuum evaporation method. After the EL layer 203 a and the chargegeneration layer 204 are formed, the light-emitting layer 213 b isformed over the hole-transport layer 212 b of the EL layer 203 b by avacuum evaporation method.

<Light-Emitting Layer>

The light-emitting layers (213, 213 a, and 213 b) each contain alight-emitting substance. Note that as the light-emitting substance, asubstance whose emission color is blue, violet, bluish violet, green,yellowish green, yellow, orange, red, or the like is appropriately used.When the plurality of light-emitting layers (213 a and 213 b) are formedusing different light-emitting substances, different emission colors canbe exhibited (for example, complementary emission colors are combined toachieve white light emission). Furthermore, a stacked-layer structure inwhich one light-emitting layer contains two or more kinds oflight-emitting substances may be employed.

The light-emitting layers (213, 213 a, and 213 b) may each contain oneor more kinds of organic compounds (a host material and an assistmaterial) in addition to a light-emitting substance (guest material). Asthe one or more kinds of organic compounds, one or both of thehole-transport material and the electron-transport material described inthis embodiment can be used.

In the light-emitting element of one embodiment of the presentinvention, it is preferable that a light-emitting substance which emitsblue light (a blue-light-emitting substance) be used as a guest materialin one of the light-emitting layers (213 a and 213 b) and a materialwhich emits green light (a green-light-emitting substance) and amaterial which emits red light (a red-light-emitting substance) be usedin the other light-emitting layer. This manner is effective in the casewhere the blue-light-emitting substance (the blue-light-emitting layer)has lower light luminous efficiency or a shorter lifetime than thematerials (layers) which emit other colors. Here, it is preferable thata light-emitting substance that converts singlet excitation energy intolight emission in the visible light range be used as theblue-light-emitting substance and light-emitting substances that converttriplet excitation energy into light emission in the visible light rangebe used as the green- and red-light-emitting substances, whereby thespectrum balance between R, G, and B is improved.

There is no particular limitation on the light-emitting substances thatcan be used for the light-emitting layers (213, 213 a, and 213 b), and alight-emitting substance that converts singlet excitation energy intolight emission in the visible light range or a light-emitting substancethat converts triplet excitation energy into light emission in thevisible light range can be used. Examples of the light-emittingsubstance are given below.

As an example of the light-emitting substance that converts singletexcitation energy into light emission, a substance that emitsfluorescence (fluorescent material) can be given. Examples of thesubstance that emits fluorescence include a pyrene derivative, ananthracene derivative, a triphenylene derivative, a fluorene derivative,a carbazole derivative, a dibenzothiophene derivative, a dibenzofuranderivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, apyridine derivative, a pyrimidine derivative, a phenanthrene derivative,and a naphthalene derivative. A pyrene derivative is particularlypreferable because it has a high emission quantum yield. Specificexamples of the pyrene derivative includeN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn),N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPrn),N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6ThAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation: 1,6BnfAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-02), andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03).

In addition, it is possible to use5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA), or the like.

As examples of a light-emitting substance that converts tripletexcitation energy into light emission, a substance that emitsphosphorescence (phosphorescent material) and a thermally activateddelayed fluorescence (TADF) material that exhibits thermally activateddelayed fluorescence can be given.

Examples of a phosphorescent material include an organometallic complex,a metal complex (platinum complex), and a rare earth metal complex.These substances exhibit the respective emission colors (emission peaks)and thus, any of them is appropriately selected according to need.

As examples of a phosphorescent material which emits blue or green lightand whose emission spectrum has a peak wavelength at greater than orequal to 450 nm and less than or equal to 570 nm, the followingsubstances can be given.

For example, organometallic complexes having a 4H-triazole skeleton,such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]),tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]), andtris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPr5btz)₃]); organometallic complexes having a1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptz1-Me)₃]); organometallic complexes having animidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); organometallic complexes in which aphenylpyridine derivative having an electron-withdrawing group is aligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)); and the like can be given.

As examples of a phosphorescent material which emits green or yellowlight and whose emission spectrum has a peak wavelength at greater thanor equal to 495 nm and less than or equal to 590 nm, the followingsubstances can be given.

For example, organometallic iridium complexes having a pyrimidineskeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]),(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving a pyridine skeleton, such as tris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato-N, C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: [Ir(bzq)₂(acac)]),tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)₃]),tris(2-phenylquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(pq)₃]), and bis(2-phenylquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(pq)₂(acac)]); organometalliccomplexes such as bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]), andbis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]) can be given.

Among the above, an organometallic complex having a pyridine skeleton(particularly, a phenylpyridine skeleton) or a pyrimidine skeleton is agroup of compounds effective for meeting the chromaticity of green inone embodiment of the present invention.

As examples of a phosphorescent material which emits yellow or red lightand whose emission spectrum has a peak wavelength at greater than orequal to 570 nm and less than or equal to 750 nm, the followingsubstances can be given.

For example, organometallic complexes having a pyrimidine skeleton, suchas(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), and(dipivaloylmethanato)bis[4,6-di(naphthalen-1-yl)pyrimidinato]iridium(III)(abbreviation: [Ir(d1npm)₂(dpm)]); organometallic complexes having apyrazine skeleton, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]),bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]),bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-KC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]),(acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C^(2′)]iridium(III)(abbreviation: [Ir(mpq)₂(acac)]),(acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C^(2′))iridium(III)(abbreviation: [Ir(dpq)₂(acac)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic complexes having apyridine skeleton, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: [PtOEP]); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]) can be given.

Among the above, an organometallic iridium complex having a pyrazineskeleton is a group of compounds effective for meeting the chromaticityof red in one embodiment of the present invention. In particular, anorganometallic iridium complex containing a cyano group (e.g.,[Ir(dmdppr-dmCP)₂(dpm)]) is preferable because it is stable.

Note that as the blue-light-emitting substance, a material whosephotoluminescence peak wavelength is greater than or equal to 430 nm andless than or equal to 470 nm, preferably greater than or equal to 430 nmand less than or equal to 460 nm may be used. As thegreen-light-emitting substance, a material whose photoluminescence peakwavelength is greater than or equal to 500 nm and less than or equal to540 nm, preferably greater than or equal to 500 nm and less than orequal to 530 nm may be used. As the red-light-emitting substance, amaterial whose photoluminescence peak wavelength is greater than orequal to 610 nm and less than or equal to 680 nm, preferably greaterthan or equal to 620 nm and less than or equal to 680 nm may be used.Note that the photoluminescence may be measured with either a solutionor a thin film.

With the parallel use of such compounds and microcavity effect, theabove chromaticity can be more easily met. Here, a transflectiveelectrode (a metal thin film portion) that is needed for obtainingmicrocavity effect preferably has a thickness greater than or equal to20 nm and less than or equal to 40 nm, and further preferably greaterthan 25 nm and less than or equal to 40 nm. However, the thicknessgreater than 40 nm possibly reduces the efficiency.

As the organic compounds (the host material and the assist material)used in the light-emitting layers (213, 213 a, and 213 b), one or morekinds of substances having a larger energy gap than the light-emittingsubstance (the guest material) are used. Note that any of thehole-transport materials listed above and the electron-transportmaterials given below may be used as the organic compounds (the hostmaterial and the assist material).

When the light-emitting substance is a fluorescent material, it ispreferable to use, as the host material, an organic compound that has ahigh energy level in a singlet excited state and has a low energy levelin a triplet excited state. For example, an anthracene derivative or atetracene derivative is preferably used. Specific examples include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA), 5,12-diphenyltetracene, and5,12-bis(biphenyl-2-yl)tetracene.

In the case where the light-emitting substance is a phosphorescentmaterial, an organic compound having triplet excitation energy (energydifference between a ground state and a triplet excited state) which ishigher than that of the light-emitting substance is preferably selectedas the host material. In that case, it is possible to use a zinc- oraluminum-based metal complex, an oxadiazole derivative, a triazolederivative, a benzimidazole derivative, a quinoxaline derivative, adibenzoquinoxaline derivative, a dibenzothiophene derivative, adibenzofuran derivative, a pyrimidine derivative, a triazine derivative,a pyridine derivative, a bipyridine derivative, a phenanthrolinederivative, an aromatic amine, a carbazole derivative, and the like.

Specific examples include metal complexes such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP),2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen), and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole(abbreviation: CO11); and aromatic amine compounds such as NPB, TPD, andBSPB.

In addition, condensed polycyclic aromatic compounds such as anthracenederivatives, phenanthrene derivatives, pyrene derivatives, chrysenederivatives, and dibenzo[g,p]chrysene derivatives can be used.Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA), YGAPA, PCAPA,N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-9H-carbazol-3-yl)amino]anthracene(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole(abbreviation: CzPA),3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), or the like can beused.

In the case where a plurality of organic compounds are used for thelight-emitting layers (213, 213 a, and 213 b), it is preferable to usecompounds that form an exciplex in combination with a light-emittingsubstance. In that case, although any of various organic compounds canbe combined appropriately to be used, to form an exciplex efficiently,it is particularly preferable to combine a compound that easily acceptsholes (hole-transport material) and a compound that easily acceptselectrons (electron-transport material). As the hole-transport materialand the electron-transport material, specifically, any of the materialsdescribed in this embodiment can be used.

The TADF material is a material that can up-convert a triplet excitedstate into a singlet excited state (i.e., reverse intersystem crossingis possible) using a little thermal energy and efficiently exhibitslight emission (fluorescence) from the singlet excited state. The TADFis efficiently obtained under the condition where the difference inenergy between the triplet excited level and the singlet excited levelis greater than or equal to 0 eV and less than or equal to 0.2 eV,preferably greater than or equal to 0 eV and less than or equal to 0.1eV. Note that “delayed fluorescence” exhibited by the TADF materialrefers to light emission having the same spectrum as normal fluorescenceand an extremely long lifetime. The lifetime is 10⁻⁶ seconds or longer,preferably 10⁻³ seconds or longer.

Examples of the TADF material include fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin, such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP).

Alternatively, a heterocyclic compound having a it-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring, suchas2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ),2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(PCCzPTzn),2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (ACRXTN),bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS), or10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (ACRSA) can beused. Note that a substance in which the π-electron rich heteroaromaticring is directly bonded to the π-electron deficient heteroaromatic ringis particularly preferable because both the donor property of theπ-electron rich heteroaromatic ring and the acceptor property of theπ-electron deficient heteroaromatic ring are increased and the energydifference between the singlet excited state and the triplet excitedstate becomes small.

Note that when a TADF material is used, the TADF material can becombined with another organic compound.

In the light-emitting element in FIG. 2D, the electron-transport layer214 a is formed over the light-emitting layer 213 a of the EL layer 203a by a vacuum evaporation method. After the EL layer 203 a and thecharge generation layer 204 are formed, the electron-transport layer 214b is formed over the light-emitting layer 213 b of the EL layer 203 b bya vacuum evaporation method.

<Electron-Transport Layer>

The electron-transport layers (214, 214 a, and 214 b) transport theelectrons, which are injected from the second electrode 202 by theelectron-injection layers (215, 215 a, and 215 b), to the light-emittinglayers (213, 213 a, and 213 b). Note that the electron-transport layers(214, 214 a, and 214 b) each contain an electron-transport material. Itis preferable that the electron-transport materials included in theelectron-transport layers (214, 214 a, and 214 b) be substances with anelectron mobility of higher than or equal to 1×10⁻⁶ cm²/Vs. Note thatother substances may also be used as long as the substances have anelectron-transport property higher than a hole-transport property.

Examples of the electron-transport material include metal complexeshaving a quinoline ligand, a benzoquinoline ligand, an oxazole ligand,and a thiazole ligand; an oxadiazole derivative; a triazole derivative;a phenanthroline derivative; a pyridine derivative; and a bipyridinederivative. In addition, a π-electron deficient heteroaromatic compoundsuch as a nitrogen-containing heteroaromatic compound can also be used.

Specifically, it is possible to use metal complexes such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), heteroaromatic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4′-tert-butylphenyl)-4-phenyl-5-(4″-biphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP), and4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), andquinoxaline derivatives and dibenzoquinoxaline derivatives such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[fh]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[/h]quinoxaline(abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[fh]quinoxaline (abbreviation: 7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[fh]quinoxaline (abbreviation:6mDBTPDBq-II).

Alternatively, a high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used.

Each of the electron-transport layers (214, 214 a, and 214 b) is notlimited to a single layer, but may be a stack of two or more layers eachcontaining any of the above substances.

In the light-emitting element in FIG. 2D, the electron-injection layer215 a is formed over the electron-transport layer 214 a of the EL layer203 a by a vacuum evaporation method. Subsequently, the EL layer 203 aand the charge generation layer 204 are formed, the components up to theelectron-transport layer 214 b of the EL layer 203 b are formed andthen, the electron-injection layer 215 b is formed thereover by a vacuumevaporation method.

<Electron-Injection Layer>

The electron-injection layers (215, 215 a, and 215 b) each contain asubstance having a high electron-injection property. Theelectron-injection layers (215, 215 a, and 215 b) can each be formedusing an alkali metal, an alkaline earth metal, or a compound thereof,such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride(CaF₂), or lithium oxide (LiO_(x)). A rare earth metal compound likeerbium fluoride (ErF₃) can also be used. Electride may also be used forthe electron-injection layers (215, 215 a, and 215 b). Examples of theelectride include a substance in which electrons are added at highconcentration to calcium oxide-aluminum oxide. Any of the substances forforming the electron-transport layers (214, 214 a, and 214 b), which aregiven above, can also be used.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layers(215, 215 a, and 215 b). Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.The organic compound here is preferably a material excellent intransporting the generated electrons; specifically, for example, theelectron-transport materials for forming the electron-transport layers(214, 214 a, and 214 b) (e.g., a metal complex or a heteroaromaticcompound) can be used. As the electron donor, a substance showing anelectron-donating property with respect to the organic compound may beused. Preferable examples are an alkali metal, an alkaline earth metal,and a rare earth metal. Specifically, lithium, cesium, magnesium,calcium, erbium, ytterbium, and the like can be given. Furthermore, analkali metal oxide and an alkaline earth metal oxide are preferable, anda lithium oxide, a calcium oxide, a barium oxide, and the like can begiven. Alternatively, a Lewis base such as magnesium oxide can be used.Further alternatively, an organic compound such as tetrathiafulvalene(abbreviation: TTF) can be used.

In the case where light obtained from the light-emitting layer 213 b isamplified in the light-emitting element illustrated in FIG. 2D, forexample, the optical path length between the second electrode 202 andthe light-emitting layer 213 b is preferably less than one fourth of thewavelength λ of light emitted from the light-emitting layer 213 b. Inthat case, the optical path length can be adjusted by changing thethickness of the electron-transport layer 214 b or theelectron-injection layer 215 b.

<Charge Generation Layer>

In the light-emitting element illustrated in FIG. 2D, the chargegeneration layer 204 has a function of injecting electrons into the ELlayer 203 a and injecting holes into the EL layer 203 b when a voltageis applied between the first electrode (anode) 201 and the secondelectrode (cathode) 202. The charge generation layer 204 may have eithera structure in which an electron acceptor (acceptor) is added to ahole-transport material or a structure in which an electron donor(donor) is added to an electron-transport material. Alternatively, bothof these structures may be stacked. Note that forming the chargegeneration layer 204 by using any of the above materials can suppress anincrease in drive voltage caused by the stack of the EL layers.

In the case where the charge generation layer 204 has a structure inwhich an electron acceptor is added to a hole-transport material, any ofthe materials described in this embodiment can be used as thehole-transport material. As the electron acceptor, it is possible to use7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like. In addition, an oxide of metals thatbelong to Group 4 to Group 8 of the periodic table can be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide,or the like is used.

In the case where the charge generation layer 204 has a structure inwhich an electron donor is added to an electron-transport material, anyof the materials described in this embodiment can be used as theelectron-transport material. As the electron donor, it is possible touse an alkali metal, an alkaline earth metal, a rare earth metal, metalsthat belong to Groups 2 and 13 of the periodic table, or an oxide orcarbonate thereof. Specifically, lithium (Li), cesium (Cs), magnesium(Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesiumcarbonate, or the like is preferably used. Alternatively, an organiccompound such as tetrathianaphthacene may be used as the electron donor.

<Substrate>

The light-emitting element described in this embodiment can be formedover any of a variety of substrates. Note that the type of the substrateis not limited to a certain type. Examples of the substrate include asemiconductor substrate (e.g., a single crystal substrate or a siliconsubstrate), an SOI substrate, a glass substrate, a quartz substrate, aplastic substrate, a metal substrate, a stainless steel substrate, asubstrate including stainless steel foil, a tungsten substrate, asubstrate including tungsten foil, a flexible substrate, an attachmentfilm, paper including a fibrous material, and a base material film.

Examples of the glass substrate include a barium borosilicate glasssubstrate, an aluminoborosilicate glass substrate, and a soda lime glasssubstrate. Examples of a flexible substrate, an attachment film, and abase material film include plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), and polyethersulfone (PES); a synthetic resin such as acrylic; polypropylene;polyester; polyvinyl fluoride; polyvinyl chloride; polyamide; polyimide;aramid; epoxy; an inorganic vapor deposition film; and paper.

For fabrication of the light-emitting element in this embodiment, avacuum process such as an evaporation method or a solution process suchas a spin coating method or an ink-jet method can be used. When anevaporation method is used, a physical vapor deposition method (PVDmethod) such as a sputtering method, an ion plating method, an ion beamevaporation method, a molecular beam evaporation method, or a vacuumevaporation method, a chemical vapor deposition method (CVD method), orthe like can be used. Specifically, the functional layers (thehole-injection layers (211 a and 211 b), the hole-transport layers (212a and 212 b), the light-emitting layers (213 a and 213 b), theelectron-transport layers (214 a and 214 b), the electron-injectionlayers (215 a and 215 b)) included in the EL layers and the chargegeneration layer 204 of the light-emitting element can be formed by anevaporation method (e.g., a vacuum evaporation method), a coating method(e.g., a dip coating method, a die coating method, a bar coating method,a spin coating method, or a spray coating method), a printing method(e.g., an ink-jet method, screen printing (stencil), offset printing(planography), flexography (relief printing), gravure printing,micro-contact printing, or nanoimprint lithography), or the like.

Note that materials that can be used for the functional layers (thehole-injection layers (211 a and 211 b), the hole-transport layers (212a and 212 b), the light-emitting layers (213 a and 213 b), theelectron-transport layers (214 a and 214 b), and the electron-injectionlayers (215 a and 215 b)) that are included in the EL layers (203 a and203 b) and the charge generation layer 204 in the light-emitting elementdescribed in this embodiment are not limited to the above materials, andother materials can be used in combination as long as the functions ofthe layers are fulfilled. For example, a high molecular compound (e.g.,an oligomer, a dendrimer, or a polymer), a middle molecular compound (acompound between a low molecular compound and a high molecular compoundwith a molecular weight of 400 to 4000), an inorganic compound (e.g., aquantum dot material), or the like can be used. The quantum dot may be acolloidal quantum dot, an alloyed quantum dot, a core-shell quantum dot,a core quantum dot, or the like.

The structures described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 3

In this embodiment, the light-emitting device of one embodiment of thepresent invention will be described with reference to FIG. 3A. Note thata light-emitting device illustrated in FIG. 3A is an active matrixlight-emitting device in which transistors (FETs) 302 are electricallyconnected to light-emitting elements (303R, 303G, 303B, and 303W) over afirst substrate 301. The plurality of light-emitting elements (303R,303G, 303B, and 303W) include a common EL layer 304 and each have amicrocavity structure in which the optical path length betweenelectrodes is adjusted depending on the emission color of thelight-emitting element. The light-emitting device is a top-emissionlight-emitting device in which light is emitted from the EL layer 304through color filters (306R, 306G, and 306B) formed on a secondsubstrate 305.

The light-emitting device illustrated in FIG. 3A is fabricated such thata first electrode 307 functions as a reflective electrode and a secondelectrode 308 functions as a transflective electrode. Note thatdescription in any of the other embodiments can be referred to asappropriate for electrode materials for the first electrode 307 and thesecond electrode 308.

In the case where the light-emitting element 303R functions as a redlight-emitting element, the light-emitting element 303G functions as agreen light-emitting element, the light-emitting element 303B functionsas a blue light-emitting element, and the light-emitting element 303Wfunctions as a white light-emitting element in FIG. 3A, for example, agap between the first electrode 307 and the second electrode 308 in thelight-emitting element 303R is adjusted to have an optical path length300R, a gap between the first electrode 307 and the second electrode 308in the light-emitting element 303G is adjusted to have an optical pathlength 300G, and a gap between the first electrode 307 and the secondelectrode 308 in the light-emitting element 303B is adjusted to have anoptical path length 300B as illustrated in FIG. 3B. Note that opticaladjustment can be performed in such a manner that a conductive layer307R is stacked over the first electrode 307 in the light-emittingelement 303R and a conductive layer 307G is stacked over the firstelectrode 307 in the light-emitting element 303G as illustrated in FIG.3B.

The second substrate 305 is provided with the color filters (306R, 306G,and 306B). Note that the color filters each transmit visible light in aspecific wavelength range and blocks visible light in a specificwavelength range. Thus, as illustrated in FIG. 3A, the color filter 306Rthat transmits only light in the red wavelength range is provided in aposition overlapping with the light-emitting element 303R, whereby redlight emission can be obtained from the light-emitting element 303R.Furthermore, the color filter 306G that transmits only light in thegreen wavelength range is provided in a position overlapping with thelight-emitting element 303G, whereby green light emission can beobtained from the light-emitting element 303G. Moreover, the colorfilter 306B that transmits only light in the blue wavelength range isprovided in a position overlapping with the light-emitting element 303B,whereby blue light emission can be obtained from the light-emittingelement 303B. Note that the light-emitting element 303W can emit whitelight without a color filter. Note that a black layer (black matrix) 309may be provided at an end portion of each color filter. The colorfilters (306R, 306G, and 306B) and the black layer 309 may be coveredwith an overcoat layer formed using a transparent material.

Although the light-emitting device in FIG. 3A has a structure in whichlight is extracted from the second substrate 305 side (top emissionstructure), a structure in which light is extracted from the firstsubstrate 301 side where the FETs 302 are formed (bottom emissionstructure) may be employed. Note that in the light-emitting devicehaving a top emission structure, the first substrate 301 can be alight-blocking substrate or a light-transmitting substrate, whereas in alight-emitting device having a bottom emission structure, the firstsubstrate 301 needs to be a light-transmitting substrate.

In FIG. 3A, the light-emitting elements are the red light-emittingelement, the green light-emitting element, the blue light-emittingelement, and the white light-emitting element; however, thelight-emitting elements of one embodiment of the present invention arenot limited to the above, and a yellow light-emitting element or anorange light-emitting element may be used. Note that description in anyof the other embodiments can be referred to as appropriate for materialsthat are used for the EL layers (a light-emitting layer, ahole-injection layer, a hole-transport layer, an electron-transportlayer, an electron-injection layer, a charge generation layer, and thelike) to fabricate each of the light-emitting elements. In that case, acolor filter needs to be appropriately selected depending on theemission color of the light-emitting element.

With the above structure, a light-emitting device includinglight-emitting elements that exhibit a plurality of emission colors canbe fabricated.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 4

In this embodiment, a light-emitting device that is one embodiment ofthe present invention will be described.

The use of the element structure of the light-emitting element of oneembodiment of the present invention allows fabrication of an activematrix light-emitting device or a passive matrix light-emitting device.Note that an active matrix light-emitting device has a structureincluding a combination of a light-emitting element and a transistor(FET). Thus, each of a passive matrix light-emitting device and anactive matrix light-emitting device is one embodiment of the presentinvention. Note that any of the light-emitting elements described inother embodiments can be used in the light-emitting device described inthis embodiment.

In this embodiment, an active matrix light-emitting device will bedescribed with reference to FIGS. 4A and 4B.

FIG. 4A is a top view illustrating the light-emitting device and FIG. 4Bis a cross-sectional view taken along chain line A-A′ in FIG. 4A. Theactive matrix light-emitting device includes a pixel portion 402, adriver circuit portion (source line driver circuit) 403, and drivercircuit portions (gate line driver circuits) (404 a and 404 b) that areprovided over a first substrate 401. The pixel portion 402 and thedriver circuit portions (403, 404 a, and 404 b) are sealed between thefirst substrate 401 and a second substrate 406 with a sealant 405.

A lead wiring 407 is provided over the first substrate 401. The leadwiring 407 is connected to an FPC 408 that is an external inputterminal. Note that the FPC 408 transmits a signal (e.g., a videosignal, a clock signal, a start signal, or a reset signal) or apotential from the outside to the driver circuit portions (403, 404 a,and 404 b). The FPC 408 may be provided with a printed wiring board(PWB). Note that the light-emitting device provided with an FPC or a PWBis included in the category of a light-emitting device.

FIG. 4B illustrates a cross-sectional structure of the light-emittingdevice.

The pixel portion 402 includes a plurality of pixels each of whichincludes an FET (switching FET) 411, an FET (current control FET) 412,and a first electrode 413 electrically connected to the FET 412. Notethat the number of FETs included in each pixel is not particularlylimited and can be set appropriately.

As FETs 409, 410, 411, and 412, for example, a staggered transistor oran inverted staggered transistor can be used without particularlimitation. A top-gate transistor, a bottom-gate transistor, or the likemay be used.

Note that there is no particular limitation on the crystallinity of asemiconductor that can be used for the FETs 409, 410, 411, and 412, andan amorphous semiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. A semiconductor having crystallinity ispreferably used, in which case deterioration of the transistorcharacteristics can be suppressed.

For the semiconductor, a Group 14 element, a compound semiconductor, anoxide semiconductor, an organic semiconductor, or the like can be used,for example. As a typical example, a semiconductor containing silicon, asemiconductor containing gallium arsenide, or an oxide semiconductorcontaining indium can be used.

The driver circuit portion 403 includes the FET 409 and the FET 410. TheFET 409 and the FET 410 may be formed with a circuit includingtransistors having the same conductivity type (either n-channeltransistors or p-channel transistors) or a CMOS circuit including ann-channel transistor and a p-channel transistor. Furthermore, a drivercircuit may be provided outside.

An end portion of the first electrode 413 is covered with an insulator414. The insulator 414 can be formed using an organic compound such as anegative photosensitive resin or a positive photosensitive resin(acrylic resin), or an inorganic compound such as silicon oxide, siliconoxynitride, or silicon nitride. The insulator 414 preferably has acurved surface with curvature at an upper end portion or a lower endportion thereof. In that case, favorable coverage with a film formedover the insulator 414 can be obtained.

An EL layer 415 and a second electrode 416 are stacked over the firstelectrode 413. The EL layer 415 includes a light-emitting layer, ahole-injection layer, a hole-transport layer, an electron-transportlayer, an electron-injection layer, a charge generation layer, and thelike.

The structure and materials described in any of the other embodimentscan be used for the components of a light-emitting element 417 describedin this embodiment. Although not illustrated, the second electrode 416is electrically connected to the FPC 408 that is an external inputterminal.

Although the cross-sectional view in FIG. 4B illustrates only onelight-emitting element 417, a plurality of light-emitting elements arearranged in a matrix in the pixel portion 402. Light-emitting elementsthat emit light of three kinds of colors (R, G, and B) are selectivelyformed in the pixel portion 402, whereby a light-emitting device capableof displaying a full-color image can be obtained. In addition to thelight-emitting elements that emit light of three kinds of colors (R, G,and B), for example, light-emitting elements that emit light of white(W), yellow (Y), magenta (M), cyan (C), and the like may be formed. Forexample, the light-emitting elements that emit light of some of theabove colors are used in combination with the light-emitting elementsthat emit light of three kinds of colors (R, G, and B), whereby effectssuch as an improvement in color purity and a reduction in powerconsumption can be achieved. Alternatively, a light-emitting devicewhich is capable of displaying a full-color image may be fabricated by acombination with color filters.

When the second substrate 406 and the first substrate 401 are bonded toeach other with the sealant 405, the FETs (409, 410, 411, and 412) andthe light-emitting element 417 over the first substrate 401 are providedin a space 418 surrounded by the first substrate 401, the secondsubstrate 406, and the sealant 405. Note that the space 418 may befilled with an inert gas (e.g., nitrogen or argon) or an organicsubstance (including the sealant 405).

An epoxy-based resin, glass frit, or the like can be used for thesealant 405. It is preferable to use a material that is permeable to aslittle moisture and oxygen as possible for the sealant 405. As thesecond substrate 406, a substrate that can be used as the firstsubstrate 401 can be similarly used. Thus, any of the various substratesdescribed in the other embodiments can be appropriately used. As thesubstrate, a glass substrate, a quartz substrate, or a plastic substratemade of fiber reinforced plastic (FRP), polyvinyl fluoride (PVF),polyester, acrylic, or the like can be used. In the case where glassfrit is used for the sealant, the first substrate 401 and the secondsubstrate 406 are preferably glass substrates in terms of adhesion.

Accordingly, the active matrix light-emitting device can be obtained.

In the case where the active matrix light-emitting device is providedover a flexible substrate, the FETs and the light-emitting element maybe directly formed over the flexible substrate; alternatively, the FETsand the light-emitting element may be formed over a substrate providedwith a separation layer and then separated at the separation layer byapplication of heat, force, laser, or the like to be transferred to aflexible substrate. For the separation layer, a stack includinginorganic films such as a tungsten film and a silicon oxide film, or anorganic resin film of polyimide or the like can be used, for example.Examples of the flexible substrate include, in addition to a substrateover which a transistor can be formed, a paper substrate, a cellophanesubstrate, an aramid film substrate, a polyimide film substrate, a clothsubstrate (including a natural fiber (e.g., silk, cotton, or hemp), asynthetic fiber (e.g., nylon, polyurethane, or polyester), a regeneratedfiber (e.g., acetate, cupra, rayon, or regenerated polyester), or thelike), a leather substrate, and a rubber substrate. With the use of anyof these substrates, an increase in durability, an increase in heatresistance, a reduction in weight, and a reduction in thickness can beachieved.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 5

In this embodiment, examples of a variety of electronic devices and anautomobile manufactured using a light-emitting device of one embodimentof the present invention will be described.

Examples of the electronic device including the light-emitting deviceare television devices (also referred to as TV or television receivers),monitors for computers and the like, cameras such as digital cameras anddigital video cameras, digital photo frames, cellular phones (alsoreferred to as mobile phones or portable telephone devices), portablegame machines, portable information terminals, audio playback devices,large game machines such as pachinko machines, and the like. Specificexamples of the electronic devices are illustrated in FIGS. 5A, 5B, 5C,5D, 5D′-1, and 5D′-2 and FIGS. 6A to 6C.

FIG. 5A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7103 is incorporated in a housing 7101.The display portion 7103 can display images and may be a touch panel(input/output device) including a touch sensor (input device). Note thatthe light-emitting device of one embodiment of the present invention canbe used for the display portion 7103. In addition, here, the housing7101 is supported by a stand 7105.

The television device 7100 can be operated with an operation switch ofthe housing 7101 or a separate remote controller 7110. With operationkeys 7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasts can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 5B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer can be manufactured using the light-emitting device of oneembodiment of the present invention for the display portion 7203. Thedisplay portion 7203 may be a touch panel (input/output device)including a touch sensor (input device).

FIG. 5C illustrates a smart watch, which includes a housing 7302, adisplay portion 7304, operation buttons 7311 and 7312, a connectionterminal 7313, a band 7321, a clasp 7322, and the like.

The display portion 7304 mounted in the housing 7302 serving as a bezelincludes a non-rectangular display region. The display portion 7304 candisplay an icon 7305 indicating time, another icon 7306, and the like.The display portion 7304 may be a touch panel (input/output device)including a touch sensor (input device).

The smart watch illustrated in FIG. 5C can have a variety of functions,such as a function of displaying a variety of information (e.g., a stillimage, a moving image, and a text image) on a display portion, a touchpanel function, a function of displaying a calendar, date, time, and thelike, a function of controlling processing with a variety of software(programs), a wireless communication function, a function of beingconnected to a variety of computer networks with a wirelesscommunication function, a function of transmitting and receiving avariety of data with a wireless communication function, and a functionof reading a program or data stored in a recording medium and displayingthe program or data on a display portion.

The housing 7302 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. Note that the smart watch can be manufacturedusing the light-emitting device for the display portion 7304.

FIG. 5D illustrates an example of a cellular phone (e.g., smartphone). Acellular phone 7400 includes a housing 7401 provided with a displayportion 7402, a microphone 7406, a speaker 7405, a camera 7407, anexternal connection portion 7404, an operation button 7403, and thelike. In the case where a light-emitting device is manufactured byforming the light-emitting element of one embodiment of the presentinvention over a flexible substrate, the light-emitting device can beused for the display portion 7402 having a curved surface as illustratedin FIG. 5D.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 5D is touched with a finger or the like, data can be input to thecellular phone 7400. In addition, operations such as making a call andcomposing e-mail can be performed by touch on the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or composing e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7402 so that characters displayed on the screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7402.

When a detection device such as a gyroscope sensor or an accelerationsensor is provided inside the cellular phone 7400, display on the screenof the display portion 7402 can be automatically changed by determiningthe orientation of the cellular phone 7400 (whether the cellular phoneis placed horizontally or vertically for a landscape mode or a portraitmode).

The screen modes are changed by touch on the display portion 7402 oroperation with the operation button 7403 of the housing 7401. The screenmodes can be switched depending on the kind of images displayed on thedisplay portion 7402. For example, when a signal of an image displayedon the display portion is a signal of moving image data, the screen modeis switched to the display mode. When the signal is a signal of textdata, the screen mode is switched to the input mode.

Moreover, in the input mode, if a signal detected by an optical sensorin the display portion 7402 is detected and the input by touch on thedisplay portion 7402 is not performed for a certain period, the screenmode may be controlled so as to be changed from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by touchon the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. In addition, by providing abacklight or a sensing light source that emits near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

The light-emitting device can be used for a cellular phone having astructure illustrated in FIG. 5D′-1 or FIG. 5D′-2, which is anotherstructure of the cellular phone (e.g., smartphone).

Note that in the case of the structure illustrated in FIG. 5D′-1 or FIG.5D′-2, text data, image data, or the like can be displayed on secondscreens 7502(1) and 7502(2) of housings 7500(1) and 7500(2) as well asfirst screens 7501(1) and 7501(2). Such a structure enables a user toeasily see text data, image data, or the like displayed on the secondscreens 7502(1) and 7502(2) while the cellular phone is placed in theuser's breast pocket.

Another electronic device including a light-emitting device is afoldable portable information terminal illustrated in FIGS. 6A to 6C.FIG. 6A illustrates a portable information terminal 9310 which isopened. FIG. 6B illustrates the portable information terminal 9310 whichis being opened or being folded. FIG. 6C illustrates the portableinformation terminal 9310 which is folded. The portable informationterminal 9310 is highly portable when folded. The portable informationterminal 9310 is highly browsable when opened because of a seamlesslarge display region.

A display portion 9311 is supported by three housings 9315 joinedtogether by hinges 9313. Note that the display portion 9311 may be atouch panel (input/output device) including a touch sensor (inputdevice). By bending the display portion 9311 at a connection portionbetween two housings 9315 with the use of the hinges 9313, the portableinformation terminal 9310 can be reversibly changed in shape from anopened state to a folded state. The light-emitting device of oneembodiment of the present invention can be used for the display portion9311. A display region 9312 in the display portion 9311 is a displayregion that is positioned at a side surface of the portable informationterminal 9310 which is folded. On the display region 9312, informationicons, file shortcuts of frequently used applications or programs, andthe like can be displayed, and confirmation of information and start ofapplication and the like can be smoothly performed.

FIGS. 7A and 7B illustrate an automobile including a light-emittingdevice. The light-emitting device can be incorporated in the automobile,and specifically, can be included in lights 5101 (including lights ofthe rear part of the car), a wheel cover 5102, a part or the whole of adoor 5103, or the like on the outer side of the automobile which isillustrated in FIG. 7A. The light-emitting device can also be includedin a display portion 5104, a steering wheel 5105, a gear lever 5106, aseat 5107, an inner rearview mirror 5108, or the like on the inner sideof the automobile which is illustrated in FIG. 7B, or in a part of aglass window.

As described above, the electronic devices and the automobile can beobtained using the light-emitting device of one embodiment of thepresent invention. Note that the light-emitting device can be used forelectronic devices and automobiles in a variety of fields without beinglimited to those described in this embodiment.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 6

In this embodiment, the structures of lighting devices fabricated usingthe light-emitting device of one embodiment of the present invention ora light-emitting element which is a part of the light-emitting devicewill be described with reference to FIGS. 8A to 8D.

FIGS. 8A to 8D are examples of cross-sectional views of lightingdevices. FIGS. 8A and 8B illustrate bottom-emission lighting devices inwhich light is extracted from the substrate side, and FIGS. 8C and 8Dillustrate top-emission lighting devices in which light is extractedfrom the sealing substrate side.

A lighting device 4000 illustrated in FIG. 8A includes a light-emittingelement 4002 over a substrate 4001. In addition, the lighting device4000 includes a substrate 4003 with unevenness on the outside of thesubstrate 4001. The light-emitting element 4002 includes a firstelectrode 4004, an EL layer 4005, and a second electrode 4006.

The first electrode 4004 is electrically connected to an electrode 4007,and the second electrode 4006 is electrically connected to an electrode4008. In addition, an auxiliary wiring 4009 electrically connected tothe first electrode 4004 may be provided. Note that an insulating layer4010 is formed over the auxiliary wiring 4009.

The substrate 4001 and a sealing substrate 4011 are bonded to each otherwith a sealant 4012. A desiccant 4013 is preferably provided between thesealing substrate 4011 and the light-emitting element 4002. Thesubstrate 4003 has the unevenness illustrated in FIG. 8A, whereby theextraction efficiency of light emitted from the light-emitting element4002 can be increased.

Instead of the substrate 4003, a diffusion plate 4015 may be provided onthe outside of the substrate 4001 as in a lighting device 4100illustrated in FIG. 8B.

A lighting device 4200 illustrated in FIG. 8C includes a light-emittingelement 4202 over a substrate 4201. The light-emitting element 4202includes a first electrode 4204, an EL layer 4205, and a secondelectrode 4206.

The first electrode 4204 is electrically connected to an electrode 4207,and the second electrode 4206 is electrically connected to an electrode4208. An auxiliary wiring 4209 electrically connected to the secondelectrode 4206 may be provided. An insulating layer 4210 may be providedunder the auxiliary wiring 4209.

The substrate 4201 and a sealing substrate 4211 with unevenness arebonded to each other with a sealant 4212. A barrier film 4213 and aplanarization film 4214 may be provided between the sealing substrate4211 and the light-emitting element 4202. The sealing substrate 4211 hasthe unevenness illustrated in FIG. 8C, whereby the extraction efficiencyof light emitted from the light-emitting element 4202 can be increased.

Instead of the sealing substrate 4211, a diffusion plate 4215 may beprovided over the light-emitting element 4202 as in a lighting device4300 illustrated in FIG. 8D.

Note that with the use of the light-emitting device of one embodiment ofthe present invention or a light-emitting element which is a part of thelight-emitting device as described in this embodiment, a lighting devicehaving desired chromaticity can be provided.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 7

In this embodiment, application examples of a lighting device fabricatedusing the light-emitting device of one embodiment of the presentinvention or a light-emitting element which is a part of thelight-emitting device will be described with reference to FIG. 9.

A ceiling light 8001 can be used as an indoor lighting device. Examplesof the ceiling light 8001 include a direct-mount light and an embeddedlight. Besides, application to a cord pendant light (light that issuspended from a ceiling by a cord) is also possible.

A foot light 8002 lights a floor so that safety on the floor can beimproved. For example, it can be effectively used in a bedroom, on astaircase, or on a passage. In that case, the size or shape of the footlight can be changed depending on the area or structure of a room.

A sheet-like lighting 8003 is a thin sheet-like lighting device. Thesheet-like lighting, which is attached to a wall when used, isspace-saving and thus can be used for a wide variety of uses.Furthermore, the area of the sheet-like lighting can be increased. Thesheet-like lighting can also be used on a wall or housing having acurved surface.

In addition, a lighting device 8004 in which the direction of light froma light source is controlled to be only a desired direction can be used.

Besides the above examples, when the light-emitting device of oneembodiment of the present invention or a light-emitting element which isa part of the light-emitting device is used as part of furniture in aroom, a lighting device that functions as the furniture can be obtained.

As described above, a variety of lighting devices that include thelight-emitting device can be obtained. Note that these lighting devicesare also embodiments of the present invention.

The structures described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 8

In this embodiment, touch panels including the light-emitting device ofone embodiment of the present invention will be described with referenceto FIGS. 10A and 10B, FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13Aand 13B, and FIG. 14.

FIGS. 10A and 10B are perspective views of a touch panel 2000. Note thatFIGS. 10A and 10B illustrate only main components of the touch panel2000 for simplicity.

The touch panel 2000 includes a display panel 2501 and a touch sensor2595 (see FIG. 10B). The touch panel 2000 includes a substrate 2510, asubstrate 2570, and a substrate 2590.

The display panel 2501 includes, over the substrate 2510, a plurality ofpixels and a plurality of wirings 2511 through which signals aresupplied to the pixels. The plurality of wirings 2511 are led to aperipheral portion of the substrate 2510, and parts of the plurality ofwirings 2511 form a terminal 2519. The terminal 2519 is electricallyconnected to an FPC 2509(1).

The substrate 2590 includes the touch sensor 2595 and a plurality ofwirings 2598 electrically connected to the touch sensor 2595. Theplurality of wirings 2598 are led to a peripheral portion of thesubstrate 2590, and parts of the plurality of wirings 2598 form aterminal 2599. The terminal 2599 is electrically connected to an FPC2509(2). Note that in FIG. 10B, electrodes, wirings, and the like of thetouch sensor 2595 provided on the back side of the substrate 2590 (theside facing the substrate 2570) are indicated by solid lines forclarity.

As the touch sensor 2595, a capacitive touch sensor can be used, forexample. Examples of the capacitive touch sensor include a surfacecapacitive touch sensor, a projected capacitive touch sensor, and thelike.

Examples of the projected capacitive touch sensor are a self-capacitivetouch sensor, a mutual capacitive touch sensor, and the like, whichdiffer mainly in the driving method. The use of a mutual capacitive typeis preferable because multiple points can be sensed simultaneously.

First, an example of using a projected capacitive touch sensor will bedescribed below with reference to FIG. 10B. Note that in the case of aprojected capacitive touch sensor, a variety of sensors that can senseproximity or touch of a sensing target such as a finger can be used.

The projected capacitive touch sensor 2595 includes electrodes 2591 andelectrodes 2592. The electrodes 2591 are electrically connected to anyof the plurality of wirings 2598, and the electrodes 2592 areelectrically connected to any of the other wirings 2598. The electrodes2592 each have a shape of a plurality of quadrangles arranged in onedirection with one corner of a quadrangle connected to one corner ofanother quadrangle with a wiring 2594, as illustrated in FIGS. 10A and10B. In the same manner, the electrodes 2591 each have a shape of aplurality of quadrangles arranged with one corner of a quadrangleconnected to one corner of another quadrangle; however, the direction inwhich the electrodes 2591 are connected is a direction crossing thedirection in which the electrodes 2592 are connected. Note that thedirection in which the electrodes 2591 are connected and the directionin which the electrodes 2592 are connected are not necessarilyperpendicular to each other, and the electrodes 2591 may be arranged tointersect with the electrodes 2592 at an angle greater than 0° and lessthan 90°.

The intersecting area of the electrode 2592 and the wiring 2594 ispreferably as small as possible. Such a structure allows a reduction inthe area of a region where the electrodes are not provided, reducingvariation in transmittance. As a result, variation in luminance of lightpassing through the touch sensor 2595 can be reduced.

Note that the shapes of the electrodes 2591 and the electrodes 2592 arenot limited thereto and can be any of a variety of shapes. For example,the plurality of electrodes 2591 may be provided so that a space betweenthe electrodes 2591 is reduced as much as possible, and the plurality ofelectrodes 2592 may be provided with an insulating layer located betweenthe electrodes 2591 and 2592. In this case, it is preferable to provide,between two adjacent electrodes 2592, a dummy electrode electricallyinsulated from these electrodes because the area of regions havingdifferent transmittances can be reduced.

Next, the touch panel 2000 will be described in detail with reference toFIGS. 11A and 11B. FIGS. 11A and 11B correspond to cross-sectional viewstaken along dashed-dotted line X1-X2 in FIG. 10A.

The touch panel 2000 includes the touch sensor 2595 and the displaypanel 2501.

The touch sensor 2595 includes the electrodes 2591 and the electrodes2592 provided in a staggered arrangement in contact with the substrate2590, an insulating layer 2593 covering the electrodes 2591 and theelectrodes 2592, and the wiring 2594 that electrically connects theadjacent electrodes 2591 to each other. Between the adjacent electrodes2591, the electrode 2592 is provided.

The electrodes 2591 and the electrodes 2592 can be formed using alight-transmitting conductive material. As the light-transmittingconductive material, an In—Sn oxide (also referred to as ITO), anIn—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, an In—W—Znoxide, or the like can be used. In addition, it is possible to use ametal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese(Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga),zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta),tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag),yttrium (Y), or neodymium (Nd) or an alloy containing an appropriatecombination of any of these metals. A graphene compound may be used aswell. When a graphene compound is used, it can be formed, for example,by reducing a graphene oxide film. As a reducing method, a method withapplication of heat, a method with laser irradiation, or the like can beemployed.

For example, the electrodes 2591 and 2592 can be formed by depositing alight-transmitting conductive material on the substrate 2590 by asputtering method and then removing an unneeded portion by any ofvarious patterning techniques such as photolithography.

Examples of a material for the insulating layer 2593 include a resinsuch as an acrylic resin or an epoxy resin, a resin having a siloxanebond, and an inorganic insulating material such as silicon oxide,silicon oxynitride, or aluminum oxide.

The adjacent electrodes 2591 are electrically connected to each otherwith the wiring 2594 formed in part of the insulating layer 2593. Notethat a material for the wiring 2594 preferably has higher conductivitythan materials for the electrodes 2591 and 2592 to reduce electricalresistance.

The wiring 2598 is electrically connected to any of the electrodes 2591and 2592. Part of the wiring 2598 functions as a terminal. For thewiring 2598, a metal material such as aluminum, gold, platinum, silver,nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper,or palladium or an alloy material containing any of these metalmaterials can be used.

Through the terminal 2599, the wiring 2598 and the FPC 2509(2) areelectrically connected to each other. The terminal 2599 can be formedusing any of various kinds of anisotropic conductive films (ACF),anisotropic conductive pastes (ACP), and the like.

An adhesive layer 2597 is provided in contact with the wiring 2594. Thatis, the touch sensor 2595 is attached to the display panel 2501 so thatthey overlap with each other with the adhesive layer 2597 providedtherebetween. Note that the substrate 2570 as illustrated in FIG. 11Amay be provided over the surface of the display panel 2501 that is incontact with the adhesive layer 2597; however, the substrate 2570 is notalways needed.

The adhesive layer 2597 has a light-transmitting property. For example,a thermosetting resin or an ultraviolet curable resin can be used;specifically, a resin such as an acrylic resin, a urethane-based resin,an epoxy-based resin, or a siloxane-based resin can be used.

The display panel 2501 in FIG. 11A includes, between the substrate 2510and the substrate 2570, a plurality of pixels arranged in a matrix and adriver circuit. Each pixel includes a light-emitting element and a pixelcircuit that drives the light-emitting element.

In FIG. 11A, a pixel 2502R is shown as an example of the pixel of thedisplay panel 2501, and a scan line driver circuit 2503 g is shown as anexample of the driver circuit.

The pixel 2502R includes a light-emitting element 2550R and a transistor2502 t that can supply electric power to the light-emitting element2550R.

The transistor 2502 t is covered with an insulating layer 2521. Theinsulating layer 2521 has a function of providing a flat surface bycovering unevenness caused by the transistor and the like that have beenalready formed. The insulating layer 2521 may serve also as a layer forpreventing diffusion of impurities. That is preferable because areduction in the reliability of the transistor or the like due todiffusion of impurities can be prevented.

The light-emitting element 2550R is electrically connected to thetransistor 2502 t through a wiring. It is one electrode of thelight-emitting element 2550R that is directly connected to the wiring.An end portion of the one electrode of the light-emitting element 2550Ris covered with an insulator 2528.

The light-emitting element 2550R includes an EL layer between a pair ofelectrodes. A coloring layer 2567R is provided to overlap with thelight-emitting element 2550R, and part of light emitted from thelight-emitting element 2550R is transmitted through the coloring layer2567R and extracted in the direction indicated by an arrow in thedrawing. A light-blocking layer 2567BM is provided at an end portion ofthe coloring layer, and a sealing layer 2560 is provided between thelight-emitting element 2550R and the coloring layer 2567R.

Note that when the sealing layer 2560 is provided on the side from whichlight from the light-emitting element 2550R is extracted, the sealinglayer 2560 preferably has a light-transmitting property. The sealinglayer 2560 preferably has a higher refractive index than the air.

The scan line driver circuit 2503 g includes a transistor 2503 t and acapacitor 2503 c. Note that the driver circuit and the pixel circuitscan be formed in the same process over the same substrate. Thus, in amanner similar to that of the transistor 2502 t in the pixel circuit,the transistor 2503 t in the driver circuit (the scan line drivercircuit 2503 g) is also covered with the insulating layer 2521.

The wirings 2511 through which a signal can be supplied to thetransistor 2503 t are provided. The terminal 2519 is provided in contactwith the wiring 2511. The terminal 2519 is electrically connected to theFPC 2509(1), and the FPC 2509(1) has a function of supplying signalssuch as an image signal and a synchronization signal. Note that aprinted wiring board (PWB) may be attached to the FPC 2509(1).

Although the case where the display panel 2501 illustrated in FIG. 11Aincludes a bottom-gate transistor is described, the structure of thetransistor is not limited thereto, and any of transistors with variousstructures can be used. In each of the transistors 2502 t and 2503 tillustrated in FIG. 11A, a semiconductor layer containing an oxidesemiconductor can be used for a channel region. Alternatively, asemiconductor layer containing amorphous silicon or a semiconductorlayer containing polycrystalline silicon that is obtained bycrystallization process such as laser annealing can be used for achannel region.

FIG. 11B illustrates the structure that includes a top-gate transistorinstead of the bottom-gate transistor illustrated in FIG. 11A. The kindof the semiconductor layer that can be used for the channel region doesnot depend on the structure of the transistor.

In the touch panel 2000 illustrated in FIG. 11A, an anti-reflectionlayer 2567 p overlapping with at least the pixel is preferably providedon a surface of the touch panel on the side from which light from thepixel is extracted, as illustrated in FIG. 11A. As the anti-reflectionlayer 2567 p, a circular polarizing plate or the like can be used.

For the substrates 2510, 2570, and 2590 in FIG. 11A, for example, aflexible material having a vapor permeability of 1×10⁻⁵ g/(m²·day) orlower, preferably 1×10⁻⁶ g/(m²·day) or lower, can be favorably used.Alternatively, it is preferable to use the materials that make thesesubstrates have substantially the same coefficient of thermal expansion.For example, the coefficients of linear expansion of the materials are1×10⁻³/K or lower, preferably 5×10⁻⁵/K or lower, and further preferably1×10⁻⁵/K or lower.

Next, a touch panel 2000′ having a structure different from that of thetouch panel 2000 illustrated in FIGS. 11A and 11B will be described withreference to FIGS. 12A and 12B. It can be used as a touch panel as wellas the touch panel 2000.

FIGS. 12A and 12B are cross-sectional views of the touch panel 2000′. Inthe touch panel 2000′ illustrated in FIGS. 12A and 12B, the position ofthe touch sensor 2595 relative to the display panel 2501 is differentfrom that in the touch panel 2000 illustrated in FIGS. 11A and 11B. Onlydifferent structures will be described below, and the above descriptionof the touch panel 2000 can be referred to for the other similarstructures.

The coloring layer 2567R overlaps with the light-emitting element 2550R.The light-emitting element 2550R illustrated in FIG. 12A emits light tothe side where the transistor 2502 t is provided. That is, (part of)light emitted from the light-emitting element 2550R passes through thecoloring layer 2567R and is extracted in the direction indicated by anarrow in FIG. 12A. Note that the light-blocking layer 2567BM is providedat an end portion of the coloring layer 2567R.

The touch sensor 2595 is provided on the transistor 2502 t side (the farside from the light-emitting element 2550R) of the display panel 2501(see FIG. 12A).

The adhesive layer 2597 is in contact with the substrate 2510 of thedisplay panel 2501 and attaches the display panel 2501 and the touchsensor 2595 to each other in the structure illustrated in FIG. 12A. Thesubstrate 2510 is not necessarily provided between the display panel2501 and the touch sensor 2595 that are attached to each other by theadhesive layer 2597.

As in the touch panel 2000, transistors with a variety of structures canbe used for the display panel 2501 in the touch panel 2000′. Although abottom-gate transistor is used in FIG. 12A, a top-gate transistor may beused as illustrated in FIG. 12B.

An example of a driving method of the touch panel will be described withreference to FIGS. 13A and 13B.

FIG. 13A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 13A illustrates a pulse voltage outputcircuit 2601 and a current sensing circuit 2602. Note that in FIG. 13A,six wirings X1 to X6 represent electrodes 2621 to which a pulse voltageis applied, and six wirings Y1 to Y6 represent electrodes 2622 thatdetect changes in current. FIG. 13A also illustrates capacitors 2603that are each formed in a region where the electrodes 2621 and 2622overlap with each other. Note that functional replacement between theelectrodes 2621 and 2622 is possible.

The pulse voltage output circuit 2601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 2621 and 2622 of the capacitor 2603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 2603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 2602 is a circuit for detecting changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 2603. No change in currentvalue is detected in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value isdetected when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for sensing of current values.

FIG. 13B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 13A. In FIG. 13B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 13B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in response to the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change uniformly in response tochanges in the voltages of the wirings X1 to X6. The current value isdecreased at the point of approach or contact of a sensing target andaccordingly the waveform of the voltage value changes. By detecting achange in mutual capacitance in this manner, the approach or contact ofa sensing target can be sensed.

Although FIG. 13A illustrates a passive-type touch sensor in which onlythe capacitor 2603 is provided at the intersection of wirings as a touchsensor, an active-type touch sensor including a transistor and acapacitor may be used. FIG. 14 illustrates an example of a sensorcircuit included in an active-type touch sensor.

The sensor circuit in FIG. 14 includes the capacitor 2603 andtransistors 2611, 2612, and 2613.

A signal G2 is input to a gate of the transistor 2613. A voltage VRES isapplied to one of a source and a drain of the transistor 2613, and oneelectrode of the capacitor 2603 and a gate of the transistor 2611 areelectrically connected to the other of the source and the drain of thetransistor 2613. One of a source and a drain of the transistor 2611 iselectrically connected to one of a source and a drain of the transistor2612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 2611. A signal G1 is input to a gate of thetransistor 2612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 2612. The voltage VSS isapplied to the other electrode of the capacitor 2603.

Next, the operation of the sensor circuit in FIG. 14 will be described.First, a potential for turning on the transistor 2613 is supplied as thesignal G2, and a potential with respect to the voltage VRES is thusapplied to a node n connected to the gate of the transistor 2611. Then,a potential for turning off the transistor 2613 is applied as the signalG2, whereby the potential of the node n is maintained. Then, mutualcapacitance of the capacitor 2603 changes owing to the approach orcontact of a sensing target such as a finger, and accordingly thepotential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 2612 issupplied as the signal G1. A current flowing through the transistor2611, that is, a current flowing through the wiring ML is changeddepending on the potential of the node n. By sensing this current, theapproach or contact of a sensing target can be sensed.

In each of the transistors 2611, 2612, and 2613, an oxide semiconductorlayer is preferably used as a semiconductor layer in which a channelregion is formed. In particular, it is preferable to use such atransistor as the transistor 2613 because the potential of the node ncan be held for a long time and the frequency of operation ofresupplying VRES to the node n (refresh operation) can be reduced.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Embodiment 9

In this embodiment, as a display device including the structure of thelight-emitting device of one embodiment of the present invention, adisplay device that includes a reflective liquid crystal element and alight-emitting element and that can display an image both in atransmissive mode and a reflective mode will be described with referenceto FIGS. 15A, 15B1, and 15B2, FIG. 16, and FIG. 17. Such a displaydevice can also be referred to as an emissive OLED and reflective LChybrid display (ER-hybrid display).

The display device described in this embodiment can be driven withextremely low power consumption for displaying an image using thereflective mode in a bright place such as outdoors. Meanwhile, in a darkplace such as indoors or in a night environment, an image with a widecolor gamut and high color reproducibility can be displayed with the useof the transmissive mode. Thus, by combination of these modes, thedisplay device can display an image with low power consumption and highcolor reproducibility as compared with the case of a conventionaldisplay panel.

As an example of the display device of this embodiment, description willbe made of a display device in which a liquid crystal element providedwith a reflective electrode and a light-emitting element are stacked andan opening in the reflective electrode is provided in a positionoverlapping with the light-emitting element. Visible light is reflectedby the reflective electrode in the reflective mode and light emittedfrom the light-emitting element is emitted through the opening in thereflective electrode in the transmissive mode. Note that transistorsused for driving these elements (the liquid crystal element and thelight-emitting element) are preferably formed on the same plane. It ispreferable that the liquid crystal element and the light-emittingelement be stacked with an insulating layer therebetween.

FIG. 15A is a block diagram illustrating a display device described inthis embodiment. A display device 3000 includes a circuit (G) 3001, acircuit (S) 3002, and a display portion 3003. In the display portion3003, a plurality of pixels 3004 are arranged in an R direction and a Cdirection in a matrix. A plurality of wirings G1, wirings G2, wiringsANO, and wirings CSCOM are electrically connected to the circuit (G)3001. These wirings are also electrically connected to the plurality ofpixels 3004 arranged in the R direction. A plurality of wirings S1 andwirings S2 are electrically connected to the circuit (S) 3002, and thesewirings are also electrically connected to the plurality of pixels 3004arranged in the C direction.

Each of the plurality of pixels 3004 includes a liquid crystal elementand a light-emitting element. The liquid crystal element and thelight-emitting element include portions overlapping with each other.

FIG. 15B1 shows the shape of a conductive film 3005 serving as areflective electrode of the liquid crystal element included in the pixel3004. Note that an opening 3007 is provided in a position 3006 which ispart of the conductive film 3005 and which overlaps with thelight-emitting element. That is, light emitted from the light-emittingelement is emitted through the opening 3007.

The pixels 3004 in FIG. 15B1 are arranged such that the adjacent pixels3004 in the R direction exhibit different colors. Furthermore, theopenings 3007 are provided so as not to be arranged in a line in the Rdirection. Such arrangement has an effect of suppressing crosstalkbetween the light-emitting elements of adjacent pixels 3004.Furthermore, there is an advantage that element formation isfacilitated.

The opening 3007 can have a polygonal shape, a quadrangular shape, anelliptical shape, a circular shape, a cross shape, a stripe shape, or aslit-like shape, for example.

FIG. 15B2 illustrates another example of the arrangement of theconductive films 3005.

The ratio of the opening 3007 to the total area of the conductive film3005 (excluding the opening 3007) affects the display of the displaydevice. That is, a problem is caused in that as the area of the opening3007 is larger, the display using the liquid crystal element becomesdarker; in contrast, as the area of the opening 3007 is smaller, thedisplay using the light-emitting element becomes darker. Furthermore, inaddition to the problem of the ratio of the opening, a small area of theopening 3007 itself also causes a problem in that extraction efficiencyof light emitted from the light-emitting element is decreased. The ratioof the opening 3007 to the total area of the conductive film 3005(excluding the opening 3007) is preferably 5% or more and 60% or lessbecause the display quality can be maintained even when the liquidcrystal element and the light-emitting element are used in acombination.

Next, an example of a circuit configuration of the pixel 3004 isdescribed with reference to FIG. 16. FIG. 16 illustrates two adjacentpixels 3004.

The pixel 3004 includes a transistor SW1, a capacitor C1, a liquidcrystal element 3010, a transistor SW2, a transistor M, a capacitor C2,a light-emitting element 3011, and the like. Note that these componentsare electrically connected to any of the wiring G1, the wiring G2, thewiring ANO, the wiring CSCOM, the wiring S1, and the wiring S2 in thepixel 3004. The liquid crystal element 3010 and the light-emittingelement 3011 are electrically connected to a wiring VCOM1 and a wiringVCOM2, respectively.

A gate of the transistor SW1 is connected to the wiring G1. One of asource and a drain of the transistor SW1 is connected to the wiring S1,and the other of the source and the drain is connected to one electrodeof the capacitor C1 and one electrode of the liquid crystal element3010. The other electrode of the capacitor C1 is connected to the wiringCSCOM. The other electrode of the liquid crystal element 3010 isconnected to the wiring VCOM1.

A gate of the transistor SW2 is connected to the wiring G2. One of asource and a drain of the transistor SW2 is connected to the wiring S2,and the other of the source and the drain is connected to one electrodeof the capacitor C2 and a gate of the transistor M. The other electrodeof the capacitor C2 is connected to one of a source and a drain of thetransistor M and the wiring ANO. The other of the source and the drainof the transistor M is connected to one electrode of the light-emittingelement 3011. Furthermore, the other electrode of the light-emittingelement 3011 is connected to the wiring VCOM2.

Note that the transistor M includes two gates between which asemiconductor is provided and which are electrically connected to eachother. With such a structure, the amount of current flowing through thetransistor M can be increased.

The on/off state of the transistor SW1 is controlled by a signal fromthe wiring G1. A predetermined potential is applied from the wiringVCOM1. Furthermore, orientation of liquid crystals of the liquid crystalelement 3010 can be controlled by a signal from the wiring Si. Apredetermined potential is applied from the wiring CSCOM.

The on/off state of the transistor SW2 is controlled by a signal fromthe wiring G2. By the difference between the potentials applied from thewiring VCOM2 and the wiring ANO, the light-emitting element 3011 canemit light. Furthermore, the conduction state of the transistor M can becontrolled by a signal from the wiring S2.

Accordingly, in the structure of this embodiment, in the case of thereflective mode, the liquid crystal element 3010 is controlled by thesignals supplied from the wiring G1 and the wiring S1 and opticalmodulation is utilized, whereby an image can be displayed. In the caseof the transmissive mode, the light-emitting element 3011 can emit lightwhen the signals are supplied from the wiring G2 and the wiring S2. Inthe case where both modes are performed at the same time, desireddriving can be performed on the basis of the signals from the wiring G1,the wiring G2, the wiring S1, and the wiring S2.

Next, specific description will be given with reference to FIG. 17, aschematic cross-sectional view of the display device 3000 described inthis embodiment.

The display device 3000 includes a light-emitting element 3023 and aliquid crystal element 3024 between substrates 3021 and 3022. Note thatthe light-emitting element 3023 and the liquid crystal element 3024 areformed with an insulating layer 3025 positioned therebetween. That is,the light-emitting element 3023 is positioned between the substrate 3021and the insulating layer 3025, and the liquid crystal element 3024 ispositioned between the substrate 3022 and the insulating layer 3025.

A transistor 3015, a transistor 3016, a transistor 3017, a coloringlayer 3028, and the like are provided between the insulating layer 3025and the light-emitting element 3023.

A bonding layer 3029 is provided between the substrate 3021 and thelight-emitting element 3023. The light-emitting element 3023 includes aconductive layer 3030 serving as one electrode, an EL layer 3031, and aconductive layer 3032 serving as the other electrode which are stackedin this order over the insulating layer 3025. In the light-emittingelement 3023 that is a bottom emission light-emitting element, theconductive layer 3032 and the conductive layer 3030 contain a materialthat reflects visible light and a material that transmits visible light,respectively. Light emitted from the light-emitting element 3023 istransmitted through the coloring layer 3028 and the insulating layer3025 and then transmitted through the liquid crystal element 3024 via anopening 3033, thereby being emitted to the outside of the substrate3022.

In addition to the liquid crystal element 3024, a coloring layer 3034, alight-blocking layer 3035, an insulating layer 3046, a structure 3036,and the like are provided between the insulating layer 3025 and thesubstrate 3022. The liquid crystal element 3024 includes a conductivelayer 3037 serving as one electrode, a liquid crystal 3038, a conductivelayer 3039 serving as the other electrode, alignment films 3040 and3041, and the like. Note that the liquid crystal element 3024 is areflective liquid crystal element and the conductive layer 3039 servesas a reflective electrode; thus, the conductive layer 3039 is formedusing a material with high reflectivity. Furthermore, the conductivelayer 3037 serves as a transparent electrode, and thus is formed using amaterial that transmits visible light. The alignment films 3040 and 3041are provided on the conductive layers 3037 and 3039 and in contact withthe liquid crystal 3038. The insulating layer 3046 is provided so as tocover the coloring layer 3034 and the light-blocking layer 3035 andserves as an overcoat. Note that the alignment films 3040 and 3041 arenot necessarily provided.

The opening 3033 is provided in part of the conductive layer 3039. Aconductive layer 3043 is provided in contact with the conductive layer3039. Since the conductive layer 3043 has a light-transmitting property,a material transmitting visible light is used for the conductive layer3043.

The structure 3036 serves as a spacer that prevents the substrate 3022from coming closer to the insulating layer 3025 than required. Thestructure 3036 is not necessarily provided.

One of a source and a drain of the transistor 3015 is electricallyconnected to the conductive layer 3030 in the light-emitting element3023. For example, the transistor 3015 corresponds to the transistor Min FIG. 16.

One of a source and a drain of the transistor 3016 is electricallyconnected to the conductive layer 3039 and the conductive layer 3043 inthe liquid crystal element 3024 through a terminal portion 3018. Thatis, the terminal portion 3018 has a function of electrically connectingthe conductive layers provided on both surfaces of the insulating layer3025. The transistor 3016 corresponds to the transistor SW1 in FIG. 16.

A terminal portion 3019 is provided in a region where the substrates3021 and 3022 do not overlap with each other. Similarly to the terminalportion 3018, the terminal portion 3019 electrically connects theconductive layers provided on both surfaces of the insulating layer3025. The terminal portion 3019 is electrically connected to aconductive layer obtained by processing the same conductive film as theconductive layer 3043. Thus, the terminal portion 3019 and an FPC 3044can be electrically connected to each other through a connection layer3045.

A connection portion 3047 is provided in part of a region where abonding layer 3042 is provided. In the connection portion 3047, theconductive layer obtained by processing the same conductive film as theconductive layer 3043 and part of the conductive layer 3037 areelectrically connected with a connector 3048. Accordingly, a signal or apotential input from the FPC 3044 can be supplied to the conductivelayer 3037 through the connector 3048.

The structure 3036 is provided between the conductive layer 3037 and theconductive layer 3043. The structure 3036 has a function of maintaininga cell gap of the liquid crystal element 3024.

As the conductive layer 3043, a metal oxide, a metal nitride, or anoxide such as an oxide semiconductor whose resistance is reduced ispreferably used. In the case of using an oxide semiconductor, a materialin which at least one of the concentrations of hydrogen, boron,phosphorus, nitrogen, and other impurities and the number of oxygenvacancies is made to be higher than those in a semiconductor layer of atransistor is used for the conductive layer 3043.

Note that the structures described in this embodiment can be combinedwith any of the structures described in the other embodiments asappropriate.

Example 1

In this example, an element structure, a fabrication method, andproperties of a light-emitting element used in the light-emitting deviceof one embodiment of the present invention will be described. Note thatFIG. 18 illustrates an element structure of light-emitting elementsdescribed in this example, and Table 1 shows specific structures. Table1 also shows color filters (CFs) combined with the light-emittingelements. A light-emitting element 1 is combined with a CF-R; alight-emitting element 2, a CF-G; and each of light-emitting elements 3and 4, a CF-B. FIG. 24 shows transmitting properties of these CFs.Chemical formulae of materials used in this example are shown below.

TABLE 1 First hole-injection First hole- Light-emitting Referencenumeral First electrode layer transport layer layer (A) Firstelectron-transport layer in FIG. 18 901 911a 912a 913a 914aLight-emitting Ag—Pd—Cu ITSO PCPPn:MoOx PCPPn *1 cgDBCzPA NBphen element1(R) (200 nm) (110 nm) (1:0.5, 10 nm) (10 nm) (10 nm) (15 nm)Light-emitting ITSO PCPPn:MoOx element 2(G) (45 nm) (1:0.5, 20 nm)Light-emitting ITSO PCPPn:MoOx element 3(B1) (10 nm) (1:0.5, 12.5 nm)Light-emitting ITSO PCPPn:MoOx element 4(B1.5) (110 nm) (1:0.5, 16 nm)Light-emitting layer (B) First electron- Charge Second Second hole-First light- Second light- Reference numeral injection layer generationlayer hole-injection layer transport layer emitting layer emitting layerin FIG. 18 915a 904 911b 912b 913(b1) 913(b2) (Notes) Light-emittingLi₂O CuPc DBT3P-II:MoOx BPAFLP *2 *3 Light-emitting element 1(R) (0.1nm) (2 nm) (1:0.5, 10 nm) (15 nm) element 1(R) Light-emittingLight-emitting element 2(G) element 2(G) Light-emitting Light-emittingelement 3(B1) element 3(B1) Light-emitting Light-emitting element4(B1.5) element 4(B1.5) Second electron- Reference numeral Secondelectron-transport layer injection layer Second electrode in FIG. 18914b 915b 903 CF Light-emitting 2mDBTBPDBq-II NBphen LiF Ag:Mg ITO CF-RLight-emitting element 1(R) (25 nm) (15 nm) (1 nm) (1:0.1, 25 nm) (70nm) element 1(R) Light-emitting CF-G Light-emitting element 2(G) element2(G) Light-emitting CF-B Light-emitting element 3(B1) element 3(B1)Light-emitting CF-B Light-emitting element 4(B1.5) element 4(B1.5) *1cgDBCzPA:1,6BnfAPrn-03 (1:0.03, 25 nm) *22mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃] (0.8:0.2:0.06, 20 nm) *32mDBTBPDBq-II:[Ir(dmdppr-P)₂(dibm)] (1:0.04, 20 nm)

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 18, a first electrode 901 over a substrate 900, afirst EL layer 902 a over the first electrode 901, a charge generationlayer 904 over the first EL layer 902 a, a second EL layer 902 b overthe charge generation layer 904, and a second electrode 903 over thesecond EL layer 902 b. Note that the light-emitting element 1 in thisexample was a light-emitting element emitting mainly red light and alsoreferred to as a light-emitting element 1(R). The light-emitting element2 was a light-emitting element emitting mainly green light and alsoreferred to as a light-emitting element 2(G). The light-emitting element3 and the light-emitting element 4 were each a light-emitting elementemitting mainly blue light and were also referred to as a light-emittingelement 3(B1) and a light-emitting element 4(B1.5), respectively.

First, the first electrode 901 was formed over the substrate 900. Theelectrode area was set to 4 mm² (2 mm×2 mm). A glass substrate was usedas the substrate 900. The first electrode 901 was formed in thefollowing manner: a 200-nm-thick alloy film of silver (Ag), palladium(Pd), and copper (Cu) (the alloy is also referred to as Ag—Pd—Cu) wasformed by a sputtering method, and an ITSO was formed by a sputteringmethod. The ITSO was formed to have a thickness of 110 nm in the case ofthe light-emitting element 1, 45 nm in the case of the light-emittingelement 2, 10 nm in the case of the light-emitting element 3, and 110 nmin the case of the light-emitting element 4. In this example, the firstelectrode 901 functioned as an anode. The first electrode 901 was areflective electrode having a function of reflecting light. In thisexample, both the light-emitting element 3 and the light-emittingelement 4 were light-emitting elements emitting blue light while havingdifferent optical path lengths between their electrodes. Thelight-emitting element 3 had an adjusted optical path length between itselectrodes of 1 wavelength and the light-emitting element 4 had anadjusted optical path length between its electrodes of 1.5 wavelengths.

As pretreatment, a surface of the substrate was washed with water,baking was performed at 200° C. for one hour, and then UV ozonetreatment was performed for 370 seconds. After that, the substrate wastransferred into a vacuum evaporation apparatus where the pressure hadbeen reduced to approximately 10⁻⁴ Pa, and was subjected to vacuumbaking at 170° C. for 60 minutes in a heating chamber of the vacuumevaporation apparatus, and then the substrate was cooled down for about30 minutes.

Next, a first hole-injection layer 911 a was formed over the firstelectrode 901. After the pressure in the vacuum evaporation apparatuswas reduced to 10⁻⁴ Pa, the first hole-injection layer 911 a was formedby co-evaporation to have a weight ratio of3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)to molybdenum oxide of 1:0.5 and to have a thickness of 10 nm for thelight-emitting element 1; 20 nm for the light-emitting element 2; 12.5nm for the light-emitting element 3; and 16 nm for the light-emittingelement 4.

Then, a first hole-transport layer 912 a was formed over the firsthole-injection layer 911 a. As the first hole-transport layer 912 a,PCPPn was deposited by evaporation to a thickness of 10 nm. Note thatthe first hole-transport layers 912 a in the first to fourthlight-emitting elements were formed in a similar manner. It will not bementioned if fabrication of the light-emitting elements had steps incommon.

Next, a light-emitting layer (A) 913 a was formed over the firsthole-transport layer 912 a.

The light-emitting layer (A) 913 a was formed to a thickness of 25 nm byco-evaporation using7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) as a host material and usingN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03) as a guest material (fluorescent material)such that the weight ratio of cgDBCzPA to 1,6BnfAPrn-03 was 1:0.03.

Next, a first electron-transport layer 914 a was formed over thelight-emitting layer (A) 913 a. The first electron-transport layer 914 awas formed in the following manner: cgDBCzPA and2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen) were sequentially deposited by evaporation to thicknesses of 10nm and 15 nm, respectively.

After that, a first electron-injection layer 915 a was formed over thefirst electron-transport layer 914 a. The first electron-injection layer915 a was formed to a thickness of 0.1 nm by evaporation of lithiumoxide (Li₂O).

Then, the charge generation layer 904 was formed over the firstelectron-injection layer 915 a. The charge generation layer 904 wasformed to a thickness of 2 nm by evaporation of copper phthalocyanine(abbreviation: CuPc).

Next, a second hole-injection layer 911 b was formed over the chargegeneration layer 904. The second hole-injection layer 911 b was formedto a thickness of 10 nm by co-evaporation such that the weight ratio of4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II) to molybdenum oxide was 1:0.5.

Then, a second hole-transport layer 912 b was formed over the secondhole-injection layer 911 b. The second hole-transport layer 912 b wasformed to a thickness of 15 nm by evaporation of4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP).

A light-emitting layer (B) 913 b was formed over the secondhole-transport layer 912 b. The light-emitting layer (B) 913 b had astacked-layer structure of a light-emitting layer (B1) 913(b 1) and alight-emitting layer (B2) 913(b 2).

The light-emitting layer (B1) 913(b 1) was formed to a thickness of 20nm by co-evaporation using2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[fh]quinoxaline(abbreviation: 2mDBTBPDBq-II) as a host material, usingN-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF) as an assist material, and usingtris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]) as a guest material (a phosphorescent material) such thatthe weight ratio of 2mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃] was 0.8:0.2:0.06.The light-emitting layer (B2) 913(b 2) was formed to a thickness of 20nm by co-evaporation using 2mDBTBPDBq-II as a host material and usingbis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]) as a guest material (aphosphorescent material), such that the weight ratio of 2mDBTBPDBq-II to[Ir(dmdppr-P)₂(dibm)] was 1:0.04.

Next, a second electron-transport layer 914 b was formed over thelight-emitting layer (B2) 913(b 2). The second electron-transport layer914 b was formed in the following manner: 2mDBTBPDBq-II and NBphen weresequentially deposited by evaporation to thicknesses of 25 nm and 15 nm,respectively.

Then, a second electron-injection layer 915 b was formed over the secondelectron-transport layer 914 b. The second electron-injection layer 915b was formed to a thickness of 1 nm by evaporation of lithium fluoride(LiF).

Then, the second electrode 903 was formed over the secondelectron-injection layer 915 b in the following manner: silver (Ag) andmagnesium (Mg) were formed to a thickness of 25 nm by co-evaporation ata volume ratio of Ag to Mg of 1:0.1, and then an indium tin oxide (ITO)was formed to a thickness of 70 nm by a sputtering method. In thisexample, the second electrode 903 functioned as a cathode. Moreover, thesecond electrode 903 was a transflective electrode having functions oftransmitting light and reflecting light.

Through the above steps, the light-emitting elements in each of whichthe EL layers were provided between a pair of electrodes over thesubstrate 900 were formed. The first hole-injection layer 911 a, thefirst hole-transport layer 912 a, the light-emitting layer (A) 913 a,the first electron-transport layer 914 a, the first electron-injectionlayer 915 a, the second hole-injection layer 911 b, the secondhole-transport layer 912 b, the light-emitting layer (B) 913 b, thesecond electron-transport layer 914 b, and the second electron-injectionlayer 915 b described above were functional layers forming the EL layersof one embodiment of the present invention. Furthermore, in all theevaporation steps in the above fabrication method, evaporation wasperformed by a resistance-heating method.

Each of the light-emitting elements formed in this example was sealedbetween the substrate 900 and a substrate 905 as illustrated in FIG. 18.The substrate 905 was provided with a color filter 906. The sealingbetween the substrate 900 and the substrate 905 was performed in such amanner that the substrate 905 was fixed to the substrate 900 with asealing material in a glove box containing a nitrogen atmosphere, asealant was applied so as to surround the light-emitting element formedover the substrate 900, and then irradiation with 365-nm ultravioletlight at 6 J/cm² was performed and heat treatment was performed at 80°C. for 1 hour.

The light-emitting elements formed in this example each have a structurein which light is emitted in the direction indicated by the arrow fromthe second electrode 903 side of the light-emitting element.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). The results are shown in FIG. 19 toFIG. 22. FIG. 23 shows emission spectra when current at a currentdensity of 2.5 mA/cm² was applied to the light-emitting elements. Theemission spectra were measured with a multi-channel spectrometer (PMA-12manufactured by Hamamatsu Photonics K.K.). As shown in FIG. 23, theemission spectrum of the light-emitting element 1 which emits red lighthas a peak at around 635 nm, the emission spectrum of the light-emittingelement 2 which emits green light has a peak at around 521 nm, and theemission spectra of the light-emitting elements 3 and 4 which emit bluelight each have a peak at around 453 nm. The spectrum shapes werenarrowed. In this example, the measurement results of light emissionobtained from a combination of light-emitting elements and color filtersare shown.

FIG. 24 shows transmission spectra of the red color filter (CF-R) usedin combination with the light-emitting element 1(R), the green colorfilter (CF-G) used in combination with the light-emitting element 2(G),and the blue color filter (CF-B) used in combination with thelight-emitting element 3(B1) or 4(B1.5). FIG. 24 shows that the 600-nmlight transmittance of the CF-R is 52%, which is lower than or equal to60%, whereas the 650-nm light transmittance of the CF-R is 89%, which ishigher than or equal to 70%. In addition, the 480-nm light transmittanceand 580-nm light transmittance of the CF-G are 26% and 52%,respectively, which are lower than or equal to 60%, whereas the 530-nmlight transmittance of the CF-G is 72%, which is higher than or equal to70%. Furthermore, the 510-nm light transmittance of the CF-B is 60%,which is lower than or equal to 60%, whereas the 450-nm lighttransmittance of the CF-B is 80%, which is higher than or equal to 70%.

The results of the chromaticities (x, y) of the light-emitting elementsformed in this example (the light-emitting elements 1 to 3) measuredwith a luminance colorimeter (BM-5A manufactured by TOPCON CORPORATION)are shown in Table 2 below. The chromaticities of the light-emittingelements 1(R), 2(G), and 3(B1) were measured at luminances ofapproximately 730 cd/m², approximately 1800 cd/m², and approximately 130cd/m², respectively. The luminance ratio is a value such that whitelight emission close to D65 (light having chromaticity coordinates of(x, y)=(0.313, 0.329)) can be obtained by summing the luminance of R,the luminance of G, and the luminance of B.

TABLE 2 x y Light-emitting 0.697 0.297 element 1(R) Light-emitting 0.1860.778 element 2(G) Light-emitting 0.142 0.046 element 3(B1)

On the basis of the results in Table 2, the BT.2020 area ratio and theBT.2020 coverage calculated from the chromaticities (x, y) were 93% and91%, respectively. Note that an area A of a triangle formed byconnecting the CIE chromaticity coordinates (x, y) of RGB which fulfillthe BT.2020 standard and an area B of a triangle formed by connectingthe CIE chromaticity coordinates (x, y) of the three light-emittingelements in this example were calculated to obtain the area ratio (B/A).The coverage is a value which represents how much percentage of theBT.2020 standard color gamut (the inside of the above triangle) can bereproduced using a combination of the chromaticities of the threelight-emitting elements in this example.

The results of the chromaticities (x, y) of the light-emitting elements1, 2, and 4 measured with a luminance colorimeter among thelight-emitting elements formed in this example are shown in Table 3below. The chromaticities of the light-emitting elements 1(R), 2(G), and4(B1.5) were measured at luminances of approximately 550 cd/m²,approximately 1800 cd/m², and approximately 130 cd/m², respectively. Theluminance ratio is a value such that white light emission close to D65can be obtained by summing the luminance of R, the luminance of G, andthe luminance of B.

TABLE 3 x y Light-emitting 0.697 0.297 element 1(R) Light-emitting 0.1860.778 element 2(G) Light-emitting 0.156 0.042 element 4(B1.5)

On the basis of the results in Table 3, the BT.2020 area ratio and theBT.2020 coverage calculated from the chromaticities (x, y) were 92% and90%, respectively. Even such a structure having improved luminousefficiency of blue light can achieve extremely wide-range colorreproducibility.

The above results show that, in this example, the light-emitting element1(R) has a chromaticity x of greater than 0.680 and less than or equalto 0.720 and a chromaticity y of greater than or equal to 0.260 and lessthan or equal to 0.320, the light-emitting element 2(G) has achromaticity x of greater than or equal to 0.130 and less than or equalto 0.250 and a chromaticity y of greater than 0.710 and less than orequal to 0.810, and each of the light-emitting element 3(B1) and thelight-emitting element 4(B1.5) has a chromaticity x of greater than orequal to 0.120 and less than or equal to 0.170 and a chromaticity y ofgreater than or equal to 0.020 and less than 0.060. The light-emittingelement 1(R) has a chromaticity x of greater than 0.680 and thus has abetter red chromaticity than the DCI-P3 standard. The light-emittingelement 2(G) has a chromaticity y of greater than 0.71 and thus has abetter green chromaticity than the DCI-P3 standard and the NTSCstandard. In addition, the light-emitting elements 3(B1) and 4(B1.5)each have a chromaticity y of less than 0.06 and thus have a better bluechromaticity than the DCI-P3 standard.

Note that the chromaticities (x, y) of the light-emitting elements 1, 2,3, and 4 calculated using the values of the emission spectra shown inFIG. 23 are (0.693, 0.303), (0.202, 0.744), (0.139, 0.056), and (0.160,0.057), respectively. Therefore, when the chromaticities of acombination of the light-emitting elements 1(R), 2(G), and 3(B1) arecalculated using the emission spectra, the BT.2020 area ratio is 86% andthe BT.2020 coverage is 84%. In addition, when the chromaticities of acombination of the light-emitting elements 1(R), 2(G), and 4(B1.5) arecalculated using the emission spectra, the BT.2020 area ratio is 84% andthe BT.2020 coverage is 82%.

Example 2

In this example, an element structure, a forming method, and propertiesof a light-emitting element used in the light-emitting device of oneembodiment of the present invention will be described. Note that FIG. 18illustrates an element structure of light-emitting elements described inthis example, and Table 4 shows specific structures. Chemical formulaeof materials used in this example are shown below. The color filterswhose transmission spectra are shown in FIG. 24 were used.

TABLE 4 First hole-injection First hole- Light-emitting Referencenumeral First electrode layer transport layer layer (A) Firstelectron-transport layer in FIG. 18 901 911a 912a 913a 914aLight-emitting Ag—Pd—Cu ITSO PCPPn:MoOx PCPPn *1 cgDBCzPA NBphen element5(R) (200 nm) (110 nm) (1:0.5, 10 nm) (10 nm) (10 nm) (15 nm)Light-emitting ITSO PCPPn:MoOx element 6(G) (45 nm) (1:0.5, 20 nm)Light-emitting ITSO PCPPn:MoOx element 7(B1) (10 nm) (1:0.5, 12.5 nm)Light-emitting ITSO PCPPn:MoOx element 8(B1.5) (110 nm) (1:0.5, 19 nm)Light-emitting layer (B) First electron- Charge Second Second hole-First light- Second light- Reference numeral injection layer generationlayer hole-injection layer transport layer emitting layer emitting layerin FIG. 18 915a 904 911b 912b 913(b1) 913(b2) (Notes) Light-emittingLi₂O CuPc DBT3P-II:MoOx BPAFLP *2 *3 Light-emitting element 5(R) (0.1nm) (2 nm) (1:0.5, 10 nm) (15 nm) element 5(R) Light-emittingLight-emitting element 6(G) element 6(G) Light-emitting Light-emittingelement 7(B1) element 7(B1) Light-emitting Light-emitting element8(B1.5) element 8(B1.5) Second electron- Reference numeral Secondelectron-transport layer injection layer Second electrode in FIG. 18914b 915b 903 CF Light-emitting 2mDBTBPDBq-II NBphen LiF Ag:Mg ITO CF-RLight-emitting element 5(R) (25 nm) (15 nm) (1 nm) (1:0.1, 30 nm) (70nm) element 5(R) Light-emitting CF-G Light-emitting element 6(G) element6(G) Light-emitting CF-B Light-emitting element 7(B1) element 7(B1)Light-emitting CF-B Light-emitting element 8(B1.5) element 8(B1.5) *1cgDBCzPA:1,6BnfAPrn-03 (1:0.03, 25 nm) *22mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃] (0.8:0.2:0.06, 20 nm) *32mDBTBPDBq-II:[Ir(dmdppr-P)₂(dibm)] (1:0.04, 20 nm)

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 18, the first electrode 901 over the substrate 900,the first EL layer 902 a over the first electrode 901, the chargegeneration layer 904 over the first EL layer 902 a, the second EL layer902 b over the charge generation layer 904, and the second electrode 903over the second EL layer 902 b as in Example 1. Note that alight-emitting element 5 in this example was a light-emitting elementemitting mainly red light and also referred to as a light-emittingelement 5(R). A light-emitting element 6 was a light-emitting elementemitting mainly green light and also referred to as a light-emittingelement 6(G). A light-emitting element 7 and a light-emitting element 8were each a light-emitting element emitting mainly blue light and werealso referred to as a light-emitting element 7(B1) and a light-emittingelement 8(B1.5), respectively.

In the light-emitting elements in this example, the thicknesses of thelayers formed in fabricating the elements were different from eachother. However, the layers can be formed in manners similar to those inExample 1 using the same materials; thus, Example 1 is referred to anddescription is omitted in this example.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). The results are shown in FIG. 25 toFIG. 28. FIG. 29 shows emission spectra when current at a currentdensity of 2.5 mA/cm² was applied to the light-emitting elements. Theemission spectra were measured with a multi-channel spectrometer (PMA-12manufactured by Hamamatsu Photonics K.K.). As shown in FIG. 29, theemission spectrum of the light-emitting element 5 which emits red lighthas a peak at around 635 nm, the emission spectrum of the light-emittingelement 6 which emits green light has a peak at around 530 nm, and theemission spectra of the light-emitting elements 7 and 8 which emit bluelight have peaks at around 464 nm and 453 nm, respectively. The spectrumshapes were narrowed. In this example, the measurement results of lightemission obtained from a combination of light-emitting elements andcolor filters are shown.

Next, the results of the chromaticities (x, y) of the light-emittingelements formed in this example (the light-emitting elements 5 to 7)measured with a luminance colorimeter (BM-5A manufactured by TOPCONCORPORATION) are shown in Table 5 below. The chromaticities of thelight-emitting elements 5(R), 6(G), and 7(B1) were measured atluminances of approximately 650 cd/m², approximately 1900 cd/m², andapproximately 140 cd/m², respectively. The luminance ratio is a valuesuch that white light emission close to D65 can be obtained by summingthe luminance of R, the luminance of G, and the luminance of B.

TABLE 5 x y Light-emitting 0.700 0.294 element 5(R) Light-emitting 0.1750.793 element 6(G) Light-emitting 0.142 0.039 element 7(B1)

On the basis of the results in Table 5, the BT.2020 area ratio and theBT.2020 coverage calculated from the chromaticities (x, y) were 97% and95%, respectively.

The results of the chromaticities (x, y) of the light-emitting elements5 to 8 among the light-emitting elements formed in this example with aluminance colorimeter are shown in Table 6 below. The chromaticities ofthe light-emitting elements 5(R), 6(G), and 8(B1.5) were measured atluminances of approximately 650 cd/m², approximately 1900 cd/m², andapproximately 170 cd/m², respectively. The luminance ratio is a valuesuch that white light emission close to D65 can be obtained by summingthe luminance of R, the luminance of G, and the luminance of B.

TABLE 6 x y Light-emitting 0.700 0.294 element 5(R) Light-emitting 0.1750.793 element 6(G) Light-emitting 0.153 0.046 element 8(B1.5)

On the basis of the results in Table 6, the BT.2020 area ratio and theBT.2020 coverage calculated from the chromaticities (x, y) were 95% and93%, respectively. Even such a structure having improved luminousefficiency of blue light can achieve extremely wide-range colorreproducibility.

The above results show that, in this example, the light-emitting element5(R) has a chromaticity x of greater than 0.680 and less than or equalto 0.720 and a chromaticity y of greater than or equal to 0.260 and lessthan or equal to 0.320, the light-emitting element 6(G) has achromaticity x of greater than or equal to 0.130 and less than or equalto 0.250 and a chromaticity y of greater than 0.710 and less than orequal to 0.810, and each of the light-emitting element 7(B1) and thelight-emitting element 8(B1.5) has a chromaticity x of greater than orequal to 0.120 and less than or equal to 0.170 and a chromaticity y ofgreater than or equal to 0.020 and less than 0.060. The light-emittingelement 6(G) has a chromaticity y of greater than 0.71, and thus has abetter green chromaticity than the DCI-P3 standard and the NTSCstandard. In addition, the light-emitting elements 7(B1) and 8(B1.5)each have a chromaticity y of less than 0.06, and thus have a betterblue chromaticity than the DCI-P3 standard.

Note that the chromaticities (x, y) of the light-emitting elements 5, 6,7, and 8 calculated using the values of the emission spectra shown inFIG. 29 are (0.696, 0.300), (0.185, 0.760), (0.140, 0.048), and (0.154,0.056), respectively. Therefore, when the chromaticities of acombination of the light-emitting elements 5(R), 6(G), and 7(B1) arecalculated using the emission spectra, the BT.2020 area ratio is 91% andthe BT.2020 coverage is 89%. In addition, when the chromaticities of acombination of the light-emitting elements 5(R), 6(G), and 8(B1.5) arecalculated using the emission spectra, the BT.2020 area ratio is 88% andthe BT.2020 coverage is 86%.

Reference Example

In this reference example, a synthesis method ofbis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]) (Structural formula (100)),which is an organometallic complex and a light-emitting substance thatcan be used for the light-emitting layer in the light-emitting elementof one embodiment of the present invention, is described. The emissionspectrum of the organometallic complex has a peak of greater than orequal to 600 nm and less than or equal to 700 nm. The structure of[Ir(dmdppr-dmCP)₂(dpm)] is shown below.

Step 1: Synthesis of 5-hydroxy-2,3-(3,5-dimethylphenyl)pyrazine

First, 5.27 g of 3,3′,5,5′-tetramethylbenzyl, 2.61 g of glycinamidehydrochloride, 1.92 g of sodium hydroxide, and 50 mL of methanol wereput into a three-necked flask equipped with a reflux pipe, and the airin the flask was replaced with nitrogen. After that, the mixture wasstirred at 80° C. for 7 hours to cause a reaction. Then, 2.5 mL of 12Mhydrochloric acid was added thereto and stirring was performed for 30minutes. Then, 2.02 g of potassium bicarbonate was added, and stirringwas performed for 30 minutes. After the resulting suspension wassubjected to suction filtration, the obtained solid was washed withwater and methanol to give an objective pyrazine derivative as milkywhite powder in a yield of 79%. A synthesis scheme of Step 1 is shown in(a-1).

Step 2: Synthesis of 5,6-bis(3,5-dimethylphenyl)pyrazin-2-yltrifluoromethanesulfonate

Next, 4.80 g of 5-hydroxy-2,3-(3,5-dimethylphenyl)pyrazine which wasobtained in Step 1, 4.5 mL of triethylamine, and 80 mL of dehydrateddichloromethane were put into a three-necked flask, and the air in theflask was replaced with nitrogen. The flask was cooled down to −20° C.Then, 3.5 mL of trifluoromethanesulfonic anhydride was dropped therein,and stirring was performed at room temperature for 17.5 hours. Afterthat, the flask was cooled down to 0° C. Then, 0.7 mL oftrifluoromethanesulfonic anhydride was further dropped therein, andstirring was performed at room temperature for 22 hours to cause areaction. To the reaction solution, 50 mL of water and 5 mL of 1Mhydrochloric acid were added and then, dichloromethane was added, sothat a substance contained in the reaction solution was extracted in thedichloromethane. A saturated aqueous solution of sodiumhydrogencarbonate and saturated saline were added to thisdichloromethane for washing. Then, magnesium sulfate was added theretofor drying. After being dried, the solution was filtered, and thefiltrate was concentrated and the obtained residue was purified bysilica gel column chromatography using toluene:hexane=1:1 (volume ratio)as a developing solvent, to give an objective pyrazine derivative asyellow oil in a yield of 96%. A synthesis scheme of Step 2 is shown in(a-2).

Step 3: Synthesis of5-(4-cyano-2,6-dimethylphenyl)-2,3-bis(3,5-dimethylphenyl)pyrazine(Abbreviation: Hdmdppr-dmCP)

Next, 2.05 g of 5,6-bis(3,5-dimethylphenyl)pyrazin-2-yltrifluoromethanesulfonate which was obtained in Step 2, 1.00 g of4-cyano-2,6-dimethylphenylboronic acid, 3.81 g of tripotassiumphosphate, 40 mL of toluene, and 4 mL of water were put into athree-necked flask, and the air in the flask was replaced with nitrogen.The mixture in the flask was degassed by being stirred under reducedpressure, 0.044 g of tris(dibenzylideneacetone)dipalladium(0) and 0.084g of tris(2,6-dimethoxyphenyl)phosphine were then added thereto, and themixture was refluxed for 7 hours. Water was added to the reactionsolution, and then toluene was added, so that the material contained inthe reaction solution was extracted in the toluene. Saturated saline wasadded to the toluene solution, and the toluene solution was washed.Then, magnesium sulfate was added thereto for drying. After being dried,the solution was filtered, and the filtrate was concentrated and theobtained residue was purified by silica gel column chromatography usinghexane:ethyl acetate=5:1 (volume ratio) as a developing solvent, to givean objective pyrazine derivative Hdmdppr-dmCP as white powder in a yieldof 90%. A synthesis scheme of Step 3 is shown in (a-3).

Step 4: Synthesis of di-μ-chloro-tetrakis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}diiridium(III)(Abbreviation: [Ir(dmdppr-dmCP)₂Cl]₂)

Next, 15 mL of 2-ethoxyethanol, 5 mL of water, 1.74 g of Hdmdppr-dmCP(abbreviation) which was obtained in Step 3, and 0.60 g of iridiumchloride hydrate (IrCl₃×H₂O) (produced by FURUYA METAL Co., Ltd.) wereput into a recovery flask equipped with a reflux pipe, and the air inthe flask was replaced with argon. After that, microwave irradiation(2.45 GHz, 100 W) was performed for an hour to cause a reaction. Thesolvent was distilled off, and then the obtained residue wassuction-filtered and washed with hexane to give a dinuclear complex[Ir(dmdppr-dmCP)₂Cl]₂ as brown powder in a yield of 89%. A synthesisscheme of Step 4 is shown in (a-4).

Step 5: Synthesis ofbis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O, O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)])

Furthermore, 30 mL of 2-ethoxyethanol, 0.96 g of [Ir(dmdppr-dmCP)₂Cl]₂that is the dinuclear complex obtained in Step 4, 0.26 g ofdipivaloylmethane (abbreviation: Hdpm), and 0.48 g of sodium carbonatewere put into a recovery flask equipped with a reflux pipe, and the airin the flask was replaced with argon. After that, microwave irradiation(2.45 GHz, 100 W) was performed for 60 minutes. Moreover, 0.13 g of Hdpmwas added thereto, and the reaction container was subjected to microwaveirradiation (2.45 GHz, 120 W) for 60 minutes to cause a reaction. Thesolvent was distilled off, and the obtained residue was purified bysilica gel column chromatography using dichloromethane and hexane as adeveloping solvent in a volume ratio of 1:1. The obtained residue wasfurther purified by silica gel column chromatography usingdichloromethane as a developing solvent, and then recrystallization wasperformed with a mixed solvent of dichloromethane and methanol to give[Ir(dmdppr-dmCP)₂(dpm)] which is the organometallic complex as redpowder in a yield of 37%. By a train sublimation method, 0.39 g of theobtained red powder was purified. The sublimation purification wascarried out at 300° C. under a pressure of 2.6 Pa with a flow rate of anargon gas at 5 mL/min. After the purification by sublimation, a redsolid, which was an objective substance, was obtained in a yield of 85%.A synthetic scheme of Step 5 is shown in (a-5).

Note that results of the analysis of the red powder obtained in Step 5by nuclear magnetic resonance spectrometry (¹H-NMR) are given below.These results revealed that [Ir(dmdppr-dmCP)₂(dpm)], which is theorganometallic complex represented by Structural Formula (100), wasobtained in this synthesis example.

¹H-NMR. δ (CD₂Cl₂): 0.91 (s, 18H), 1.41 (s, 6H), 1.95 (s, 6H), 2.12 (s,12H), 2.35 (s, 12H), 5.63 (s, 1H), 6.49 (s, 2H), 6.86 (s, 2H), 7.17 (s,2H), 7.34 (s, 4H), 7.43 (s, 4H), 8.15 (s, 2H).

Example 3

In this example, an element structure, a fabrication method, andproperties of a light-emitting element used in the light-emitting deviceof one embodiment of the present invention will be described. Note thatFIG. 30 illustrates an element structure of light-emitting elementsdescribed in this example, and Table 7 shows specific structures.Chemical formulae of materials used in this example are shown below.Note that “ote tha the table represents an alloy film of silver (Ag),palladium (Pd), and copper (Cu) (i.e., an Ag—Pd—Cu film).

TABLE 7 Hole- Light- Electron- First Hole-injection transport emittinginjection electrode layer layer layer Electron-transport layer layerSecond electrode Light-emitting APC\ITO DBT3P-II:MoOx BPAFLP *2mDBTBPDBq-II NBphen LiF Ag:Mg ITO element 9(R) (10 nm) (1:0.5, 15 nm)(15 nm) (30 nm) (20 nm) (1 nm) (1:0.1, 30 nm) (70 nm) Light-emittingAPC\ITO DBT3P-II:MoOx BPAFLP ** 2mDBTBPDBq-II Bphen LiF Ag:Mg ITOelement 10(G) (110 nm) (1:0.5, 25 nm) (15 nm) (15 nm) (15 nm) (1 nm)(1:0.1, 30 nm) (70 nm) Light-emitting APC\ITO PCPPn:MoOx PCPPn ***cgDBCzPA Nbphen LiF Ag:Mg ITO element 11(B) (85 nm) (1:0.5, 37.5 nm) (15nm) (5 nm) (15 nm) (1 nm) (1:0.1, 30 nm) (70 nm) *2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-P)₂(dibm)] (0.7:0.3:0.04 (20nm)\0.8:0.2:0.04 (20 nm)) ** 2mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃](0.7:0.3:0.06 (20 nm)\0.8:0.2:0.06 (20 nm)) *** cgDBCzPA:1,6BnfAPrn-03(1:0.03 (25 nm))

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 30, a first electrode 1901 over a substrate 1900, anEL layer 1902 over the first electrode 1901, and a second electrode 1903over the EL layer 1902. In the EL layer 1902, a hole-injection layer1911, a hole-transport layer 1912, a light-emitting layer 1913, anelectron-transport layer 1914, and an electron-injection layer 1915 arestacked in this order from the first electrode 1901 side. Note that alight-emitting element 9 in this example was a light-emitting elementemitting mainly red light and also referred to as a light-emittingelement 9(R). A light-emitting element 10 was a light-emitting elementemitting mainly green light and also referred to as a light-emittingelement 10(G). A light-emitting element 11 was a light-emitting elementemitting mainly blue light and also referred to as a light-emittingelement 11(B).

The light-emitting elements described in this example have elementstructures different from those of the light-emitting elements describedin Examples 1 and 2. Meanwhile, functional layers included in thelight-emitting elements can be formed in a manner similar to thatdescribed in Example 1; thus, Example 1 is referred to and thedescription is omitted in this example.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). The results are shown in FIG. 31 toFIG. 34. FIG. 35 shows emission spectra when current at a currentdensity of 2.5 mA/cm² was applied to the light-emitting elements. Theemission spectra were measured with a multi-channel spectrometer (PMA-12manufactured by Hamamatsu Photonics K.K.). As shown in FIG. 35, theemission spectrum of the light-emitting element 9 which emits red lighthas a peak at around 632 nm, the emission spectrum of the light-emittingelement 10 which emits green light has a peak at around 524 nm, and theemission spectrum of the light-emitting element 11 which emits bluelight has a peak at around 462 nm. The spectrum shapes were narrowed.

Table 8 below shows the chromaticities (x, y) of the light-emittingelements (the light-emitting elements 9, 10, and 11) fabricated in thisexample measured with a luminance colorimeter (BM-5AS, manufactured byTOPCON CORPORATION). Note that the chromaticities of the light-emittingelements were measured at a luminance of approximately 1000 cd/m². FIG.36 shows the CIE1931 chromaticity coordinates (x,y chromaticitycoordinates) listed in Table 8.

TABLE 8 x y Light-emitting 0.705 0.295 element 9(R) Light-emitting 0.1740.794 element 10(G) Light-emitting 0.141 0.041 element 11(B)

Although the chromaticities (x, y) of the light-emitting elementsobtained here are chromaticities on the CIE1931 chromaticity coordinates(x,y chromaticity coordinates) as described above, chromaticities on theCIE1976 chromaticity coordinates (u′,v′ chromaticity coordinates), whichare defined so that the perceived color differences may correspond todistances equivalent in the color space, can be obtained with the use ofthe following conversion equations (1).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\mspace{625mu}} & \; \\\left. \begin{matrix}{u^{\prime} = {4\;{x/\left( {{12\; y} - {2\; x} + 3} \right)}}} \\{v^{\prime} = {9\;{y/\left( {{12\; y} - {2\; x} + 3} \right)}}}\end{matrix} \right\} & (1)\end{matrix}$

The chromaticities of the light-emitting elements in this example on theCIE1976 chromaticity coordinates (u′,v′ chromaticity coordinates) arelisted in Table 9 below. Table 9 also shows the chromaticity coordinatesin accordance with the BT.2020 standard for comparison.

TABLE 9 Example 3 BT.2020 u′ v′ u′ v′ R 0.552 0.517 0.557 0.517 G 0.0570.587 0.056 0.587 B 0.174 0.120 0.159 0.126

The BT.2020 area ratio calculated from the chromaticities (u′, v′) inTable 9 was 100%. FIG. 37 shows the chromaticity coordinates listed inTable 9.

According to the above results, the use of the light-emitting elementsdescribed in this example can offer extremely wide-range colorreproducibility.

Example 4

In this example, an element structure and properties of a light-emittingelement used in the light-emitting device of one embodiment of thepresent invention will be described. Note that FIG. 30 illustrates anelement structure of light-emitting elements described in this example,and Table 10 shows specific structures. Chemical formulae of materialsused in this example are shown below.

TABLE 10 Hole- Light- Electron- First Hole-injection transport emittinginjection electrode layer layer layer Electron-transport layer layerSecond electrode Light-emitting APC\ITO DBT3P-II:MoOx BPAFLP *2mDBTBPDBq-II NBphen LiF Ag:Mg ITO element 12(R) (120 nm) (1:0.5, 60 nm)(15 nm) (30 nm) (20 nm) (1 nm) (1:0.1, 25 nm) (70 nm) Light-emittingAPC\ITO DBT3P-II:MoOx BPAFLP ** 2mDBTBPDBq-II Bphen LiF Ag:Mg ITOelement 13(G) (110 nm) (1:0.5, 25 nm) (15 nm) (15 nm) (15 nm) (1 nm)(1:0.1, 25 nm) (70 nm) Light-emitting APC\ITO PCPPn:MoOx PCPPn ***cgDBCzPA NBphen LiF Ag:Mg ITO element 14(B) (85 nm) (1:0.5, 37.5 nm) (15nm) (5 nm) (15 nm) (1 nm) (1:0.1, 25 nm) (70 nm) Comparative APC\ITODBT3P-II:MoOx BPAFLP **** 2mDBTBPDBq-II Bphen LiF Ag:Mg ITOlight-emitting (110 nm) (1:0.5, 70 nm) (15 nm) (15 nm) (15 nm) (1 nm)(1:0.1, 25 nm) (70 nm) element 15(R) Comparative APC\ITO PCPPn:MoOxPCPPn ***** cgDBCzPA NBphen LiF Ag:Mg ITO light-emitting (85 nm) (1:0.5,37.5 nm) (15 nm) (5 nm) (15 nm) (1 nm) (1:0.1, 25 nm) (70 nm) element16(B) * 2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-P)₂(dibm)] (0.7:0.3:0.04 (20nm)\0.8:0.2:0.04 (20 nm)) ** 2mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃](0.7:0.3:0.06 (20 nm)\0.8:0.2:0.06 (20 nm)) *** cgDBCzPA:1,6BnfAPrn-03(1:0.03 (25 nm)) **** 2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-dmp)₂(dpm)](0.7:0.3:0.06 (20 nm)\0.8:0.2:0.06 (20 nm)) *****cgDBCzPA:1,6mMemFLPAPrn (1:0.03 (25 nm))

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 30, the first electrode 1901 over the substrate1900, the EL layer 1902 over the first electrode 1901, and the secondelectrode 1903 over the EL layer 1902. In the EL layer 1902, thehole-injection layer 1911, the hole-transport layer 1912, thelight-emitting layer 1913, the electron-transport layer 1914, and theelectron-injection layer 1915 are stacked in this order from the firstelectrode 1901 side. Note that a light-emitting element 12 and acomparative light-emitting element 15 described in this example werelight-emitting elements that mainly emit red light and also referred toas a light-emitting element 12(R) and a comparative light-emittingelement 15(R), respectively. A light-emitting element 13 was alight-emitting element that mainly emits green light and also referredto as a light-emitting element 13(G). A light-emitting element 14 and acomparative light-emitting element 16 were light-emitting elements thatmainly emit blue light and also referred to as a light-emitting element14(B) and a comparative light-emitting element 16(B), respectively.

The light-emitting elements described in this example had elementstructures different from those of the light-emitting elements describedin Examples 1 to 3. Meanwhile, functional layers included in thelight-emitting elements can be formed in a manner similar to thatdescribed in Example 1; thus, Example 1 is referred to and thedescription is omitted in this example.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). The results are shown in FIG. 38 toFIG. 41.

Table 11 shows initial values of main characteristics of thelight-emitting elements at around 1000 cd/m².

TABLE 11 Current Current Power External Voltage Current densityChromaticity Luminance efficiency efficiency quantum (V) (mA) (mA/cm²)(x, y) (cd/m²) (cd/A) (lm/W) efficiency (%) Light-emitting 3.2 0.10 2.4(0.711, 0.289) 900 38 37 44 element 12(R) Light-emitting 2.7 0.04 1.1(0.183, 0.786) 1100 99 110 24 element 13(G) Light-emitting 3.3 1.20 29(0.141, 0.044) 1100 3.6 3.5 6.9 element 14(B) Comparative 2.9 0.04 0.95(0.670, 0.331) 840 88 96 48 light-emitting element 15(R) Comparative 3.20.70 17 (0.138, 0.072) 1000 5.8 5.8 8.7 light-emitting element 16(B)

FIG. 42 shows emission spectra when current at a current density of 2.5mA/cm² was applied to the light-emitting elements. The emission spectrawere measured with a multi-channel spectrometer (PMA-12 produced byHamamatsu Photonics K.K.). As shown in FIG. 42, the emission spectrum ofthe light-emitting element 12 which emits red light has a peak around635 nm, the emission spectrum of the light-emitting element 13 whichemits green light has a peak around 525 nm, and the emission spectrum ofthe light-emitting element 14 which emits blue light has a peak ataround 462 nm. The spectrum shapes were narrowed. Furthermore, theemission spectrum of the comparative light-emitting element 15 has apeak at around 612 nm, and the emission spectrum of the comparativelight-emitting element 16 has a peak at around 467 nm.

Here, three types of top-emission panels (a panel 1, a panel 2, and apanel 3) each of which was formed by combination of the light-emittingelements listed in Table 11 were assumed. Table 12 shows the simulationresults obtained when a white color at D65 and 300 cd/m² is assumed tobe displayed entirely under the following conditions: an aperture ratiois 15% (5% for each of the R, G, and B pixels) and attenuation of lightby a circular polarizing plate or the like is 60%.

TABLE 12 Panel 2 Panel 3 R: Comparative R: Light- light-emittingemitting Panel 1 element 15(R) element 12(R) R: Light-emitting G: Light-G: Light- element 12(R) emitting emitting G: Light-emitting element13(G) element 13(G) element 13(G) B: Light- B: Comparative B:Light-emitting emitting light-emitting element 14(B) element 14(B)element 16(B) Structure x y x y x y Chromaticity R 0.713 0.287 0.6700.330 0.713 0.287 G 0.182 0.786 0.182 0.786 0.182 0.786 B 0.141 0.0450.141 0.045 0.138 0.072 BT.2020 area ratio 101 83 89 (CIE (u′, v′)) (%)Luminance of R 73 92 74 panel (cd/m²) G 209 191 192 B 18 18 29 Luminancein R 3671 4586 3720 pixel (cd/m²) G 10450 9533 9834 B 879 881 1446Voltage (V) R 4.0 3.5 4.0 G 3.4 3.4 3.4 B 3.2 3.2 3.2 Current R 36.586.4 36.5 efficiency G 95.3 95.6 95.5 (cd/A) B 3.7 3.7 5.8 Powerconsumption 7.7 6.5 7.8 (mW/cm²)

As shown in Table 12, the BT.2020 area ratio of the panel 1 formed bythe combination of the light-emitting elements 12(R), 13(G), and 14(B)is 101% when being calculated from the chromaticities of thelight-emitting elements on the CIE1976 chromaticity coordinates (u′,v′chromaticity coordinates), which were obtained from the chromaticitiesin Table 11. The BT.2020 area ratio of the panel 2 formed by thecombination of the comparative light-emitting element 15(R) and thelight-emitting elements 13(G) and 14(B) is 83%, and the BT.2020 arearatio of the panel 3 formed by the combination of the light-emittingelements 12(R) and 13(G) and the comparative light-emitting element16(B) is 89%. FIG. 55 is a chromaticity diagram showing thechromaticities of the light-emitting elements 12(R), 13(G), and 14(B)and the comparative light-emitting elements 15(R) and 16(B) on theCIE1976 chromaticity coordinates (u′,v′ chromaticity coordinates).

According to the above results, the use of the light-emitting elementsdescribed in this example can offer extremely wide-range colorreproducibility.

Reliability tests were performed on the light-emitting elements. FIG. 43shows results of the reliability tests. In FIG. 43, the vertical axisrepresents normalized luminance (%) with an initial luminance of 100%,and the horizontal axis represents driving time (h) of the elements.Note that in the reliability tests, the light-emitting elements weredriven under the conditions where the initial luminance was set to 300cd/m² and the current density was constant.

The results in FIG. 43 indicate that the reliability of thelight-emitting element 12(R) is as high as that of the comparativelight-emitting element 15(R) even though the light-emitting element12(R) has higher current density than the comparative light-emittingelement 15(R). The results also indicate that the light-emitting element14(B) has higher reliability than the comparative light-emitting element16(B).

Example 5

In this example, an element structure and properties of a light-emittingelement used in the light-emitting device of one embodiment of thepresent invention will be described. Note that FIG. 30 illustrates anelement structure of light-emitting elements described in this example,and Table 13 shows specific structures. Chemical formulae of materialsused in this example are shown below.

TABLE 13 Hole- Light- Electron- First Hole-injection transport emittinginjection Second electrode layer layer layer Electron-transport layerlayer electrode Light-emitting ITO DBT3P-II:MoOx BPAFLP * 2mDBTBPDBq-IINBphen LiF Al element 17(R) (70 nm) (1:0.5, 75 nm) (20 nm) (30 nm) (15nm) (1 nm) (200 nm) Light-emitting ** element 18(R) *2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-dmp)₂(dpm)] (0.7:0.3:0.06 (20nm)\0.8:0.2:0.06 (20 nm)) ** 2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-P)₂(dibm)](0.7:0.3:0.06 (20 nm)\0.8:0.2:0.06 (20 nm))

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 30, the first electrode 1901 over the substrate1900, the EL layer 1902 over the first electrode 1901, and the secondelectrode 1903 over the EL layer 1902. In the EL layer 1902, thehole-injection layer 1911, the hole-transport layer 1912, thelight-emitting layer 1913, the electron-transport layer 1914, and theelectron-injection layer 1915 are stacked in this order from the firstelectrode 1901 side. Note that a light-emitting element 17 and acomparative light-emitting element 18 in this example were each alight-emitting element emitting mainly red light.

The light-emitting elements described in this example had elementstructures different from those of the light-emitting elements describedin Examples 1 to 4. Meanwhile, functional layers included in thelight-emitting elements can be formed in a manner similar to thatdescribed in Example 1; thus, Example 1 is referred to and thedescription is omitted in this example.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). Table 14 shows initial values of maincharacteristics of the light-emitting elements at around 1000 cd/m².

TABLE 14 Current Current Power External Voltage Current densityChromaticity Luminance efficiency efficiency quantum (V) (mA) (mA/cm²)(x, y) (cd/m²) (cd/A) (lm/W) efficiency (%) Light-emitting 3.6 0.23 5.8(0.709, 0.290) 940 16.2 14 27.4 element 17(R) Comparative 3.3 0.13 3.1(0.669, 0.331) 1100 34.2 33 29.9 light-emitting element 18(R)

FIG. 44 shows emission spectra when current at a current density of 2.5mA/cm² was applied to the light-emitting elements. The emission spectrawere measured with a multi-channel spectrometer (PMA-12 manufactured byHamamatsu Photonics K.K.). The emission spectrum of a light-emittingelement 17(R) has a peak wavelength at around 642 nm, and the full widthat half maximum (FWHM) is 62 nm. The emission spectrum of a comparativelight-emitting element 18(R) has a peak wavelength at around 612 nm, andthe full width at half maximum (FWHM) is 62 nm. The light-emittingelement 17(R) and the comparative light-emitting element 18(R) havesimilar spectrum shapes.

FIG. 45 shows the CIE1931 chromaticity coordinates (x,y chromaticitycoordinates) of the light-emitting element 17(R) and the comparativelight-emitting element 18(R). FIG. 45 indicates that the light-emittingelement 17(R) meets the chromaticity of red in the BT.2020 standard.

FIG. 46 shows the relationships between external quantum efficiency andcurrent density of the light-emitting element 17(R) and the comparativelight-emitting element 18(R). The elements show similar results.

Driving tests were conducted on the light-emitting element 17(R) and thecomparative light-emitting element 18(R) with a driving current of 50mA/cm². FIG. 47 shows the results obtained when the tests were conductedat room temperature (25° C.) and FIG. 48 shows the results obtained whenthe tests were conducted at a high temperature (85° C.). The resultsindicate that the light-emitting element 17(R) can be driven for 1200hours at room temperature (25° C.) until the normalized luminance isreduced to 50% while the comparative light-emitting element 18(R) can bedriven for 500 hours, which reveals that the lifetime of thelight-emitting element 17(R) is approximately 2.4 times as long as thatof the comparative light-emitting element 18(R). The results alsoindicate that the light-emitting element 17(R) can be driven for 210hours at a high temperature (85° C.) until the normalized luminance isreduced to 50% while the comparative light-emitting element 18(R) can bedriven for 75 hours, which reveals that the lifetime of thelight-emitting element 17(R) is approximately 3 times as long as that ofthe comparative light-emitting element 18(R). Thus, it is found that thelight-emitting element 17(R) has smaller temperature dependence oflifetime than the comparative light-emitting element 18(R).

In addition, the comparison result of the driving time of thelight-emitting element 17(R) until the normalized luminance is reducedto 50% in FIG. 47 and FIG. 48 indicates that the lifetime when driven ata high temperature (85° C.) is only approximately ⅕ shorter than thelifetime when driven at room temperature (25° C.). This means that thelight-emitting element 17(R) has favorable heat resistance and has along lifetime even at high temperatures.

FIG. 49 shows the results of preservation test at high temperatures forthe light-emitting element 17(R). As apparent from FIG. 49, even whenthe light-emitting element 17(R) is preserved at a high temperature (85°C.) for 200 hours, the luminance change is small (maximum of 1.5%) andthe driving voltage change is small (maximum of 0.05%).

Example 6

In this example, an element structure and properties of a light-emittingelement used in the light-emitting device of one embodiment of thepresent invention will be described. Note that FIG. 30 illustrates anelement structure of light-emitting elements described in this example,and Table 15 shows specific structures. Chemical formulae of materialsused in this example are shown below.

TABLE 15 Hole- Light- Electron- First Hole-injection transport emittingElectron-transport injection Second electrode layer layer layer layerlayer electrode Light-emitting ITO PCPPn:MoOx PCPPn * cgDBCzPA NBphenLiF Al element 19(B) (70 nm) (4:2, 10 nm) (30 nm) (15 nm) (10 nm) (1 nm)(200 nm) Light-emitting PCPPn ** element 20(B) (25 nm) *cgDBCzPA:1,6BnfAPrn-03 (1:0.03 (25 nm)) ** cgDBCzPA:1,6mMemFLPAPrn(1:0.03 (25 nm))

<<Fabrication of Light-Emitting Elements>>

Light-emitting elements described in this example each included, asillustrated in FIG. 30, the first electrode 1901 over the substrate1900, the EL layer 1902 over the first electrode 1901, and the secondelectrode 1903 over the EL layer 1902. In the EL layer 1902, thehole-injection layer 1911, the hole-transport layer 1912, thelight-emitting layer 1913, the electron-transport layer 1914, and theelectron-injection layer 1915 are stacked in this order from the firstelectrode 1901 side. Note that a light-emitting element 19 and acomparative light-emitting element 20 in this example were each alight-emitting element emitting mainly blue light.

The light-emitting elements described in this example had elementstructures different from those of the light-emitting elements describedin Examples 1 to 5. Meanwhile, functional layers included in thelight-emitting elements can be formed in a manner similar to thatdescribed in Example 1; thus, Example 1 is referred to and thedescription is omitted in this example.

<<Operation Characteristics of Light-Emitting Elements>>

Operation characteristics of the formed light-emitting elements weremeasured. Note that the measurement was performed at room temperature(in an atmosphere kept at 25° C.). Table 16 shows initial values of maincharacteristics of the light-emitting elements at around 1000 cd/m².

TABLE 16 Current Current Power External Voltage Current densityChromaticity Luminance efficiency efficiency quantum (V) (mA) (mA/cm²)(x, y) (cd/m²) (cd/A) (lm/W) efficiency (%) Light-emitting 3.1 0.36 9.0(0.140, 0.115) 940 10.4 11 10.8 element 19(B) Comparative 3.1 0.28 7.1(0.137, 0.177) 1100 15.7 16 12.7 light-emitting element 20(B)

FIG. 50 shows emission spectra when current at a current density of 12.5mA/cm² was applied to the light-emitting elements. The emission spectrawere measured with a multi-channel spectrometer (PMA-12 manufactured byHamamatsu Photonics K.K.). The emission spectrum of a light-emittingelement 19(B) has a peak wavelength at around 458 nm, and the emissionspectrum of a comparative light-emitting element 20(B) has a peakwavelength at around 468 nm. The results show that blue light emittedfrom the light-emitting element 19(B) is deeper than that emitted fromthe comparative light-emitting element 20(B).

FIG. 51 shows the relationships between external quantum efficiency andluminance of the light-emitting element 19(B) and the comparativelight-emitting element 20(B). The results show that the light-emittingelement 19(B) has lower external quantum efficiency than the comparativelight-emitting element 20(B). This is because the fluorescence quantumyield of the light-emitting element 19(B) (77%) is lower than thefluorescence quantum yield of the comparative light-emitting element20(B) (90%) by approximately 10%.

Driving tests were conducted on the light-emitting element 19(B) and thecomparative light-emitting element 20(B) with a driving current of 50mA/cm². FIG. 52 shows the results obtained when the tests were conductedat room temperature (25° C.) and FIG. 53 shows the results obtained whenthe tests were conducted at a high temperature (85° C.). The resultsindicate that the light-emitting element 19(B) can be driven forapproximately 500 hours at room temperature (25° C.) until thenormalized luminance is reduced to 80% while the comparativelight-emitting element 20(B) can drive for approximately 200 hours,which reveals that the lifetime of the light-emitting element 19(B) isapproximately 2.5 times as long as that of the comparativelight-emitting element 20(B). The results also indicate that thelight-emitting element 19(B) can be driven for 82 hours at a hightemperature (85° C.) until the normalized luminance is reduced to 80%while the comparative light-emitting element 20(B) can be driven for 29hours, which reveals that the lifetime of the light-emitting element19(B) is approximately 2.8 times as long as that of the comparativelight-emitting element 20(B). Thus, it is found that the light-emittingelement 19(B) has smaller temperature dependence of lifetime than thecomparative light-emitting element 20(B).

In addition, the comparison result of the driving time of thelight-emitting element 19(B) until the normalized luminance is reducedto 80% in FIG. 52 and FIG. 53 indicates that the lifetime when driven ata high temperature (85° C.) is only approximately ⅙ shorter than thelifetime when driven at room temperature (25° C.). This means that thelight-emitting element 19(B) has favorable heat resistance and has along lifetime even at high temperatures.

FIG. 54 shows the results of preservation test at high temperatures forthe light-emitting element 19(B). As apparent from FIG. 54, even whenthe light-emitting element 19(B) is preserved at a high temperature (85°C.) for 250 hours, the luminance change and the driving voltage changeare small (maximum of 0.8%).

REFERENCE NUMERALS

101: first electrode, 102: second electrode, 103: EL layer, 103R: ELlayer, 103G: EL layer, 103B: EL layer, 104R: color filter, 104G: colorfilter, 104B: color filter, 105R: first light-emitting element, 105G:second light-emitting element, 105B: third light-emitting element, 106R:red light, 106G: green light, 106B: blue light, 201: first electrode,202: second electrode, 203: EL layer, 203 a: EL layer, 203 b: EL layer,204: charge generation layer, 211: hole-injection layer, 211 a:hole-injection layer, 211 b: hole-injection layer, 212: hole-transportlayer, 212 a: hole-transport layer, 212 b: hole-transport layer, 213:light-emitting layer, 213 a: light-emitting layer, 213 b: light-emittinglayer, 214: electron-transport layer, 214 a: electron-transport layer,214 b: electron-transport layer, 215: electron-injection layer, 215 a:electron-injection layer, 215 b: electron-injection layer, 301: firstsubstrate, 302: transistor (FET), 303: light-emitting element, 303R:light-emitting element, 303G: light-emitting element, 303B:light-emitting element, 303W: light-emitting element, 304: EL layer,305: second substrate, 306R: color filter, 306G: color filter, 306B:color filter, 307: first electrode, 308: second electrode, 309: blacklayer (black matrix), 401: first substrate, 402: pixel portion, 403:driver circuit portion, 404 a: driver circuit portion, 404 b: drivercircuit portion, 405: sealant, 406: second substrate, 407: lead wiring,408: flexible printed circuit (FPC), 409: FET, 410: FET, 411: FET(switching FET), 412: FET (current control FET), 413: first electrode,414: insulator, 415: EL layer, 416: second electrode, 417:light-emitting element, 418: space, 900: substrate, 901: firstelectrode, 902 a: first EL layer, 902 b: second EL layer, 903: secondelectrode, 904: charge generation layer, 905: substrate, 906: colorfilter, 911 a: first hole-injection layer, 911 b: second hole-injectionlayer, 912 a: first hole-transport layer, 912 b: second hole-transportlayer, 913 a: light-emitting layer (A), 913(b 1): light-emitting layer(B1), 913(b 2): light-emitting layer (B2), 914 a: firstelectron-transport layer, 914 b: second electron-transport layer, 915 a:first electron-injection layer, 915 b: second electron-injection layer,1900: substrate, 1901: first electrode, 1902: EL layer, 1903: secondelectrode, 1911: hole-injection layer, 1912: hole-transport layer, 1913:light-emitting layer, 1914: electron-transport layer, 1915:electron-injection layer, 2000: touch panel, 2501: display panel, 2502R:pixel, 2502 t: transistor, 2503 c: capacitor, 2503 g: scan line drivercircuit, 2503 t: transistor, 2509: FPC, 2510: substrate, 2511: wiring,2519: terminal, 2521: insulating layer, 2528: insulator, 2550R:light-emitting element, 2560: sealing layer, 2567BM: light-blockinglayer, 2567 p: anti-reflection layer, 2567R: coloring layer, 2570:substrate, 2590: substrate, 2591: electrode, 2592: electrode, 2593:insulating layer, 2594: wiring, 2595: touch sensor, 2597: adhesivelayer, 2598: wiring, 2599: terminal, 2601: pulse voltage output circuit,2602: current sensing circuit, 2603: capacitor, 2611: transistor, 2612:transistor, 2613: transistor, 2621: electrode, 2622: electrode, 3000:display device, 3001: circuit (G), 3002: circuit (S), 3003: displayportion, 3004: pixel, 3005: conductive film, 3007: opening, 3010: liquidcrystal element, 3011: light-emitting element, 3015: transistor, 3016:transistor, 3017: transistor, 3018: terminal portion, 3019: terminalportion, 3021: substrate, 3022: substrate, 3023: light-emitting element,3024: liquid crystal element, 3025: insulating layer, 3028: coloringlayer, 3029: adhesive layer, 3030: conductive layer, 3031: EL layer,3032: conductive layer, 3033: opening, 3034: coloring layer, 3035:light-blocking layer, 3036: structure, 3037: conductive layer, 3038:liquid crystal, 3039: conductive layer, 3040: alignment film, 3041:alignment film, 3042: adhesive layer, 3043: conductive layer, 3044: FPC,3045: connection layer, 3046: insulating layer, 3047: connectionportion, 3048: connector, 4000: lighting device, 4001: substrate, 4002:light-emitting element, 4003: substrate, 4004: electrode, 4005: ELlayer, 4006: electrode, 4007: electrode, 4008: electrode, 4009:auxiliary wiring, 4010: insulating layer, 4011: sealing substrate, 4012:sealant, 4013: desiccant, 4015: diffusion plate, 4100: lighting device,4200: lighting device, 4201: substrate, 4202: light-emitting element,4204: electrode, 4205: EL layer, 4206: electrode, 4207: electrode, 4208:electrode, 4209: auxiliary wiring, 4210: insulating layer, 4211: sealingsubstrate, 4212: sealant, 4213: barrier film, 4214: planarization film,4215: diffusion plate, 4300: lighting device, 5101: light, 5102: wheel,5103: door, 5104: display portion, 5105: steering wheel, 5106: gearlever, 5107: seat, 5108: inner rearview mirror, 7100: television device,7101: housing, 7103: display portion, 7105: stand, 7107: displayportion, 7109: operation key, 7110: remote controller, 7201: main body,7202: housing, 7203: display portion, 7204: keyboard, 7205: externalconnection port, 7206: pointing device, 7302: housing, 7304: displayportion, 7305: icon, 7306: icon, 7311: operation button, 7312: operationbutton, 7313: connection terminal, 7321: band, 7322: clasp, 7400: mobilephone, 7401: housing, 7402: display portion, 7403: operation button,7404: external connection portion, 7405: speaker, 7406: microphone,7407: camera, 7500(1): housing, 7500(2): housing, 7501(1): first screen,7501(2): first screen, 7502(1): second screen, 7502(2): second screen,8001: ceiling light, 8002: foot light, 8003: sheet-like lighting, 8004:lighting device, 9310: portable information terminal, 9311: displayportion, 9312: display region, 9313: hinge, and 9315: housing.

This application is based on Japanese Patent Application Serial No.2016-101783 filed with Japan Patent Office on May 20, 2016, JapanesePatent Application Serial No. 2016-178920 filed with Japan Patent Officeon Sep. 13, 2016, and Japanese Patent Application Serial No. 2016-231618filed with Japan Patent Office on Nov. 29, 2016, the entire contents ofwhich are hereby incorporated by reference.

The invention claimed is:
 1. A light-emitting device comprising: a firstlight-emitting element, a second light-emitting element, and a thirdlight-emitting element, wherein each of the first light-emittingelement, the second light-emitting element, and the third light-emittingelement comprises a pair of electrodes and an EL layer between the pairof electrodes, wherein at least one of the EL layer in the firstlight-emitting element and the EL layer in the second light-emittingelement contains a phosphorescent substance, wherein light emitted fromthe first light-emitting element has, on CIE1931 chromaticitycoordinates, a chromaticity x of greater than 0.680 and less than orequal to 0.720 and a chromaticity y of greater than or equal to 0.260and less than or equal to 0.320, wherein light emitted from the secondlight-emitting element has, on the CIE1931 chromaticity coordinates, achromaticity x of greater than or equal to 0.130 and less than or equalto 0.250 and a chromaticity y of greater than 0.710 and less than orequal to 0.810, and wherein light emitted from the third light-emittingelement has, on the CIE1931 chromaticity coordinates, a chromaticity xof greater than or equal to 0.120 and less than or equal to 0.170 and achromaticity y of greater than or equal to 0.020 and less than 0.060. 2.The light-emitting device according to claim 1, wherein the EL layer inthe third light-emitting element contains a fluorescent substance. 3.The light-emitting device according to claim 1, wherein in each of thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element, one of the pair of electrodes is areflective electrode and the other of the pair of electrodes is atransflective electrode, wherein an optical path length between thereflective electrode and the transflective electrode in the firstlight-emitting element is set so that emission intensity of red lightcan be increased, wherein an optical path length between the reflectiveelectrode and the transflective electrode in the second light-emittingelement is set so that emission intensity of green light can beincreased, and wherein an optical path length between the reflectiveelectrode and the transflective electrode in the third light-emittingelement is set so that emission intensity of blue light can beincreased.
 4. The light-emitting device according to claim 1, wherein anarea of a triangle formed by connecting CIE 1931 chromaticitycoordinates of the light emitted from the first light-emitting element,the light emitted from the second light-emitting element, and the lightemitted from the third light-emitting element is 80% or more and 100% orless of an area of a triangle formed by connecting CIE 1931 chromaticitycoordinates of red, green, and blue of a BT.2020 standard.
 5. Anelectronic device comprising: the light-emitting device according toclaim 1; and an operation key, a speaker, a microphone, or an externalconnection portion.
 6. A light-emitting device comprising: a pluralityof light-emitting elements including a first light-emitting element, asecond light-emitting element, and a third light-emitting element; afirst color filter overlapping the first light-emitting element; asecond color filter overlapping the second light-emitting element; and athird color filter overlapping the third light-emitting element, whereineach of the first light-emitting element, the second light-emittingelement, and the third light-emitting element comprises a pair ofelectrodes and an EL layer between the pair of electrodes, wherein theEL layer is shared by the first light-emitting element, the secondlight-emitting element, and the third light-emitting element and emitswhite light, wherein light obtained from the first light-emittingelement through the first color filter has, on CIE1931 chromaticitycoordinates, a chromaticity x of greater than 0.680 and less than orequal to 0.720 and a chromaticity y of greater than or equal to 0.260and less than or equal to 0.320, wherein light obtained from the secondlight-emitting element through the second color filter has, on theCIE1931 chromaticity coordinates, a chromaticity x of greater than orequal to 0.130 and less than or equal to 0.250 and a chromaticity y ofgreater than 0.710 and less than or equal to 0.810, and wherein lightobtained from the third light-emitting element through the third colorfilter has, on the CIE1931 chromaticity coordinates, a chromaticity x ofgreater than or equal to 0.120 and less than or equal to 0.170 and achromaticity y of greater than or equal to 0.020 and less than 0.060. 7.The light-emitting device according to claim 6, wherein in each of thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element, one of the pair of electrodes is areflective electrode and the other of the pair of electrodes is atransflective electrode, wherein an optical path length between thereflective electrode and the transflective electrode in the firstlight-emitting element is set so that emission intensity of red lightcan be increased, wherein an optical path length between the reflectiveelectrode and the transflective electrode in the second light-emittingelement is set so that emission intensity of green light can beincreased, and wherein an optical path length between the reflectiveelectrode and the transflective electrode in the third light-emittingelement is set so that emission intensity of blue light can beincreased.
 8. The light-emitting device according to claim 6, whereinthe EL layer comprises a first EL layer, a second EL layer, and a chargegeneration layer between the first EL layer and the second EL layer,wherein the first EL layer contains a red light-emitting substance and agreen light-emitting substance, and wherein the second EL layer containsa blue light-emitting substance.
 9. The light-emitting device accordingto claim 8, wherein at least one of the red light-emitting substance andthe green light-emitting substance is a phosphorescent substance, andwherein the blue light-emitting substance is a fluorescent substance.10. The light-emitting device according to claim 6, wherein the firstcolor filter has a 600-nm light transmittance of less than or equal to60% and a 650-nm light transmittance of greater than or equal to 70%,wherein the second color filter has a 480-nm light transmittance of lessthan or equal to 60%, a 580-nm light transmittance of less than or equalto 60%, and a 530-nm light transmittance of greater than or equal to70%, and wherein the third color filter has a 510-nm light transmittanceof less than or equal to 60% and a 450-nm light transmittance of greaterthan or equal to 70%.
 11. The light-emitting device according to claim6, wherein the light obtained from the first light-emitting elementthrough the first color filter has an emission spectrum whose peak valueis within a range from 620 nm to 680 nm.
 12. The light-emitting deviceaccording to claim 6, wherein an area of a triangle formed by connectingCIE 1931 chromaticity coordinates of the light emitted from the firstlight-emitting element, the light emitted from the second light-emittingelement, and the light emitted from the third light-emitting element is80% or more and 100% or less of an area of a triangle formed byconnecting CIE 1931 chromaticity coordinates of red, green, and blue ofa BT.2020 standard.
 13. An electronic device comprising: thelight-emitting device according to claim 6; and an operation key, aspeaker, a microphone, or an external connection portion.